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<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">class</span> <span class="token class-name">Hello</span> <span class="token punctuation">{</span>
</span><span class="code-line">  <span class="token comment">// main method</span>
</span><span class="code-line">  <span class="token keyword">static</span> <span class="token return-type class-name"><span class="token keyword">void</span></span> <span class="token function">Main</span><span class="token punctuation">(</span><span class="token class-name"><span class="token keyword">string</span><span class="token punctuation">[</span><span class="token punctuation">]</span></span> args<span class="token punctuation">)</span>
</span><span class="code-line">  <span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token comment">// 输出: Hello, world!</span>
</span><span class="code-line">    Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token string">"Hello, world!"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">  <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
<p>编译运行（确保在项目目录下）</p>
<pre class="language-shell"><code class="language-shell code-highlight"><span class="code-line">$ dotnet run
</span><span class="code-line">Hello, world<span class="token operator">!</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="命名空间"><a aria-hidden="true" tabindex="-1" href="#命名空间"><span class="icon icon-link"></span></a>命名空间</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">//使用时 using 命名名称</span>
</span><span class="code-line"><span class="token keyword">using</span> <span class="token namespace">Test</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">//创建：</span>
</span><span class="code-line"><span class="token keyword">namespace</span> <span class="token namespace">Test</span><span class="token punctuation">{</span>
</span><span class="code-line">  <span class="token keyword">class</span> <span class="token class-name">Test_className</span><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token comment">// main方法是程序的主入口</span>
</span><span class="code-line">    <span class="token keyword">public</span> <span class="token return-type class-name"><span class="token keyword">void</span></span> <span class="token function">Myclass</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
</span><span class="code-line">      console<span class="token punctuation">.</span><span class="token function">writeline</span><span class="token punctuation">(</span><span class="token string">"Test"</span><span class="token punctuation">)</span>
</span><span class="code-line">    <span class="token punctuation">}</span>
</span><span class="code-line">  <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="访问修饰符"><a aria-hidden="true" tabindex="-1" href="#访问修饰符"><span class="icon icon-link"></span></a>访问修饰符</h3><div class="wrap-body">
<!--rehype:wrap-class=row-span-2-->

































<table class="style-list"><thead><tr><th>声明的可访问性</th><th>含义</th></tr></thead><tbody><tr><td><code>public</code></td><td>访问不受限制</td></tr><tr><td><code>protected</code></td><td>访问限于包含类或派生自包含类的类型 (该类内部和继承类中可以访问)</td></tr><tr><td><code>internal</code></td><td>访问限于当前程序集</td></tr><tr><td><code>protected internal</code></td><td>访问限于当前程序集或派生自包含类的类型</td></tr><tr><td><code>private</code></td><td>访问限于包含类</td></tr><tr><td><code>private protected</code></td><td>访问限于包含类或当前程序集中派生自包含类的类型,自 C# 7.2 之后可用</td></tr></tbody></table>
<!--rehype:className=style-list-->
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="字符串"><a aria-hidden="true" tabindex="-1" href="#字符串"><span class="icon icon-link"></span></a>字符串</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> first <span class="token operator">=</span> <span class="token string">"John"</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> last <span class="token operator">=</span> <span class="token string">"Doe"</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">// 字符串连接</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> name <span class="token operator">=</span> first <span class="token operator">+</span> <span class="token string">" "</span> <span class="token operator">+</span> last<span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>name<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// => John Doe</span>
</span></code></pre>
<p>查看: <a href="#c-%E5%AD%97%E7%AC%A6%E4%B8%B2">C#字符串</a></p>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="注释"><a aria-hidden="true" tabindex="-1" href="#注释"><span class="icon icon-link"></span></a>注释</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 单行注释</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">/* 
</span></span><span class="code-line"><span class="token comment"> * 多行
</span></span><span class="code-line"><span class="token comment"> * 注释 - 用于文档 
</span></span><span class="code-line"><span class="token comment"> */</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// TODO：</span>
</span><span class="code-line"><span class="token comment">// 向IDE中的任务列表添加注释（VS、Rider都支持）</span>
</span><span class="code-line"><span class="token doc-comment comment">/// XML 单行注释，用于文档</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="用户输入"><a aria-hidden="true" tabindex="-1" href="#用户输入"><span class="icon icon-link"></span></a>用户输入</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-2-->
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line line-number" line="1">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token string">"Enter number:"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line line-number" line="2"><span class="token keyword">if</span><span class="token punctuation">(</span><span class="token keyword">int</span><span class="token punctuation">.</span><span class="token function">TryParse</span><span class="token punctuation">(</span>Console<span class="token punctuation">.</span><span class="token function">ReadLine</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token keyword">out</span> <span class="token class-name"><span class="token keyword">int</span></span> input<span class="token punctuation">)</span><span class="token punctuation">)</span>
</span><span class="code-line line-number" line="3"><span class="token punctuation">{</span>
</span><span class="code-line line-number" line="4">  <span class="token comment">// 输入验证</span>
</span><span class="code-line line-number" line="5">  Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token interpolation-string"><span class="token string">$"You entered </span><span class="token interpolation"><span class="token punctuation">{</span><span class="token expression language-csharp">input</span><span class="token punctuation">}</span></span><span class="token string">"</span></span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line line-number" line="6"><span class="token punctuation">}</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="条件判断"><a aria-hidden="true" tabindex="-1" href="#条件判断"><span class="icon icon-link"></span></a>条件判断</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">int</span></span> j <span class="token operator">=</span> <span class="token number">10</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span>j <span class="token operator">==</span> <span class="token number">10</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
</span><span class="code-line">  Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token string">"I get printed"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token keyword">if</span> <span class="token punctuation">(</span>j <span class="token operator">></span> <span class="token number">10</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
</span><span class="code-line">  Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token string">"I don't"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
</span><span class="code-line">  Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token string">"I also don't"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="变量"><a aria-hidden="true" tabindex="-1" href="#变量"><span class="icon icon-link"></span></a>变量</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">int</span></span> intNum <span class="token operator">=</span> <span class="token number">9</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">long</span></span> longNum <span class="token operator">=</span> <span class="token number">9999999</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">float</span></span> floatNum <span class="token operator">=</span> <span class="token number">9.99F</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">double</span></span> doubleNum <span class="token operator">=</span> <span class="token number">99.999</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">decimal</span></span> decimalNum <span class="token operator">=</span> <span class="token number">99.9999M</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">char</span></span> letter <span class="token operator">=</span> <span class="token char">'D'</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> @<span class="token keyword">bool</span> <span class="token operator">=</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> site <span class="token operator">=</span> <span class="token string">"jaywcjlove.github.io"</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> num <span class="token operator">=</span> <span class="token number">999</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> str <span class="token operator">=</span> <span class="token string">"999"</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> bo <span class="token operator">=</span> <span class="token boolean">false</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist col-span-2 row-span-2"><div class="wrap-header h3wrap"><h3 id="循环"><a aria-hidden="true" tabindex="-1" href="#循环"><span class="icon icon-link"></span></a>循环</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-2 row-span-2-->
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span></span> numbers <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token keyword">for</span><span class="token punctuation">(</span><span class="token class-name"><span class="token keyword">int</span></span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&#x3C;</span> numbers<span class="token punctuation">.</span>Length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
</span><span class="code-line">  Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>numbers<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
<hr>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">foreach</span><span class="token punctuation">(</span><span class="token class-name"><span class="token keyword">int</span></span> num <span class="token keyword">in</span> numbers<span class="token punctuation">)</span> <span class="token punctuation">{</span>
</span><span class="code-line">  Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>num<span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
<hr>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">while</span><span class="token punctuation">(</span><span class="token boolean">true</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">   Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token string">"只要给定的条件为真，while 循环语句会重复执行"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
<hr>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">do</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">   Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token string">"与 while 类似，do...while 会确保至少执行一次循环。"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span> <span class="token keyword">while</span><span class="token punctuation">(</span> <span class="token boolean">true</span> <span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="数组"><a aria-hidden="true" tabindex="-1" href="#数组"><span class="icon icon-link"></span></a>数组</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">char</span><span class="token punctuation">[</span><span class="token punctuation">]</span></span> chars <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name"><span class="token keyword">char</span></span><span class="token punctuation">[</span><span class="token number">10</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
</span><span class="code-line">chars<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token char">'a'</span><span class="token punctuation">;</span>
</span><span class="code-line">chars<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token char">'b'</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span><span class="token punctuation">[</span><span class="token punctuation">]</span></span> letters <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token string">"A"</span><span class="token punctuation">,</span> <span class="token string">"B"</span><span class="token punctuation">,</span> <span class="token string">"C"</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span></span> mylist <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token number">100</span><span class="token punctuation">,</span> <span class="token number">200</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span><span class="token punctuation">[</span><span class="token punctuation">]</span></span> answers <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token boolean">true</span><span class="token punctuation">,</span> <span class="token boolean">false</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="c-数据类型"><a aria-hidden="true" tabindex="-1" href="#c-数据类型"><span class="icon icon-link"></span></a>C# 数据类型</h2><div class="wrap-body">
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="原始数据类型"><a aria-hidden="true" tabindex="-1" href="#原始数据类型"><span class="icon icon-link"></span></a>原始数据类型</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-2-->














































































































<table class="show-header"><thead><tr><th>关键字</th><th>名称</th><th>System 别名</th><th>占用空间（Byte）</th><th>数据范围</th></tr></thead><tbody><tr><td><code>bool</code></td><td>布尔型</td><td><code>Boolean</code></td><td>1</td><td>true/false</td></tr><tr><td><code>sbyte</code></td><td>有符号字节型</td><td><code>SByte</code></td><td>1</td><td>-128 ~ 127</td></tr><tr><td><code>byte</code></td><td>字节型</td><td><code>Byte</code></td><td>1</td><td>0 ~ 255</td></tr><tr><td><code>short</code></td><td>短整型</td><td><code>Int16</code></td><td>2</td><td>-32,768 ~ 32,767</td></tr><tr><td><code>ushort</code></td><td>无符号短整型</td><td><code>UInt16</code></td><td>2</td><td>0 ~ 65,535</td></tr><tr><td><code>int</code></td><td>整型</td><td><code>Int32</code></td><td>4</td><td>-2,147,483,648 ~ 2,147,483,647</td></tr><tr><td><code>uint</code></td><td>无符号整型</td><td><code>UInt32</code></td><td>4</td><td>0 ~ 4,294,967,295</td></tr><tr><td><code>long</code></td><td>长整型</td><td><code>Int64</code></td><td>8</td><td>-2^63 ~ 2^63-1</td></tr><tr><td><code>ulong</code></td><td>无符号长整型</td><td><code>UInt64</code></td><td>8</td><td>0 ~ 2^64-1</td></tr><tr><td><code>char</code></td><td>字符型</td><td><code>Char</code></td><td>8</td><td>UTF-16 所编码的字符</td></tr><tr><td><code>float</code></td><td>单精度浮点型</td><td><code>Single</code></td><td>4</td><td>±1.5x10^45 ~ ±3.4x10^38</td></tr><tr><td><code>double</code></td><td>双精度浮点型</td><td><code>Double</code></td><td>8</td><td>±5.0x10^-324 ~ ±1.7x10^308</td></tr><tr><td><code>nint</code></td><td>指针型</td><td><code>IntPtr</code></td><td>与指针相同</td><td>与指针相同（受操作系统和处理器位宽影响）</td></tr><tr><td><code>nuint</code></td><td>无符号指针型</td><td><code>UIntPtr</code></td><td>与指针相同</td><td>与指针相同（受操作系统和处理器位宽影响）</td></tr></tbody></table>
<!--rehype:className=show-header-->
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="基本数据类型"><a aria-hidden="true" tabindex="-1" href="#基本数据类型"><span class="icon icon-link"></span></a>基本数据类型</h3><div class="wrap-body">





























<table class="show-header"><thead><tr><th align="left">关键字</th><th>名称</th><th>System 别名</th><th>说明</th></tr></thead><tbody><tr><td align="left">(除指针型外的全部原始数据类型)</td><td>-</td><td>-</td><td>原始数据类型都是值类型，基本数据类型包含部分本质上是引用的数据类型</td></tr><tr><td align="left"><code>string</code></td><td>字符串</td><td><code>String</code></td><td>可变长度</td></tr><tr><td align="left"><code>decimal</code></td><td>十进制浮点数</td><td><code>Decimal</code></td><td>适合处理货币等计算，16字节长，不遵循 IEEE 754 关于浮点数的规则</td></tr></tbody></table>
<!--rehype:className=show-header-->
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="c-字符串"><a aria-hidden="true" tabindex="-1" href="#c-字符串"><span class="icon icon-link"></span></a>C# 字符串</h2><div class="wrap-body">
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="字符串连接"><a aria-hidden="true" tabindex="-1" href="#字符串连接"><span class="icon icon-link"></span></a>字符串连接</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> first <span class="token operator">=</span> <span class="token string">"John"</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> last <span class="token operator">=</span> <span class="token string">"Doe"</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> name <span class="token operator">=</span> first <span class="token operator">+</span> <span class="token string">" "</span> <span class="token operator">+</span> last<span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>name<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// => John Doe</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="字符串插值"><a aria-hidden="true" tabindex="-1" href="#字符串插值"><span class="icon icon-link"></span></a>字符串插值</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> first <span class="token operator">=</span> <span class="token string">"John"</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> last <span class="token operator">=</span> <span class="token string">"Doe"</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> name <span class="token operator">=</span> <span class="token interpolation-string"><span class="token string">$"</span><span class="token interpolation"><span class="token punctuation">{</span><span class="token expression language-csharp">first</span><span class="token punctuation">}</span></span><span class="token string"> </span><span class="token interpolation"><span class="token punctuation">{</span><span class="token expression language-csharp">last</span><span class="token punctuation">}</span></span><span class="token string">"</span></span><span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>name<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// => John Doe</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="字符串成员"><a aria-hidden="true" tabindex="-1" href="#字符串成员"><span class="icon icon-link"></span></a>字符串成员</h3><div class="wrap-body">
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<table class="show-header"><thead><tr><th align="left">成员</th><th>说明</th></tr></thead><tbody><tr><td align="left"><code>Length</code></td><td>返回字符串长度的属性</td></tr><tr><td align="left"><code>Compare()</code></td><td>比较两个字符串的静态方法</td></tr><tr><td align="left"><code>Contains()</code></td><td>确定字符串是否包含特定的子字符串</td></tr><tr><td align="left"><code>Equals()</code></td><td>确定两个字符串是否具有相同的字符数据</td></tr><tr><td align="left"><code>Format()</code></td><td>通过 {0} 表示法和使用其他原语格式化字符串</td></tr><tr><td align="left"><code>Trim()</code></td><td>从尾随和前导字符中删除特定字符的所有实例。 默认删除前导和尾随空格</td></tr><tr><td align="left"><code>Split()</code></td><td>删除提供的字符并从两侧的剩余字符中创建一个数组</td></tr></tbody></table>
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</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="逐字字符串"><a aria-hidden="true" tabindex="-1" href="#逐字字符串"><span class="icon icon-link"></span></a>逐字字符串</h3><div class="wrap-body">
<pre class="wrap-text"><code class="language-cs code-highlight"><span class="code-line line-number" line="1"><span class="token class-name"><span class="token keyword">string</span></span> longString <span class="token operator">=</span> <span class="token string">@"I can type any characters in here !#@$%^&#x26;*()__+ '' \n \t except double quotes and I will be taken literally. I even work with multiple lines."</span><span class="token punctuation">;</span>
</span></code></pre>
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</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="成员示例"><a aria-hidden="true" tabindex="-1" href="#成员示例"><span class="icon icon-link"></span></a>成员示例</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 使用 System.String 的属性</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> lengthOfString <span class="token operator">=</span> <span class="token string">"How long?"</span><span class="token punctuation">;</span>
</span><span class="code-line">lengthOfString<span class="token punctuation">.</span>Length           <span class="token comment">// => 9</span>
</span><span class="code-line"><span class="token comment">// 使用 System.String 的方法</span>
</span><span class="code-line">lengthOfString<span class="token punctuation">.</span><span class="token function">Contains</span><span class="token punctuation">(</span><span class="token string">"How"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// => true</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="频繁字符串拼接"><a aria-hidden="true" tabindex="-1" href="#频繁字符串拼接"><span class="icon icon-link"></span></a>频繁字符串拼接</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> sb <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">StringBuilder</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token class-name"><span class="token keyword">int</span></span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&#x3C;</span> <span class="token number">100</span><span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    sb<span class="token punctuation">.</span><span class="token function">Append</span><span class="token punctuation">(</span>i<span class="token punctuation">.</span><span class="token function">ToString</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>sb<span class="token punctuation">.</span><span class="token function">ToString</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">// => 123456789....</span>
</span></code></pre>
<p>对于频繁拼接字符串的场景（如：成百上千次循环），使用 <code>System.Text.StringBuilder</code> 提升性能</p>
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="原始字符串文本"><a aria-hidden="true" tabindex="-1" href="#原始字符串文本"><span class="icon icon-link"></span></a>原始字符串文本</h3><div class="wrap-body">
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<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// C#11 语法, 至少3个双引号(""")开头和结尾，内容可以输入任何原始字符</span>
</span><span class="code-line"><span class="token comment">// 单行: 左引号，右引号，内容 三者同行</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> singleLine <span class="token operator">=</span> <span class="token string">""</span>"Content begin <span class="token string">"Hello World!"</span> end<span class="token punctuation">.</span><span class="token string">""</span>"<span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 多行：左引号，右引号各一行，内容需与右引号缩进对齐</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> multiLine <span class="token operator">=</span> <span class="token string">""</span>"
</span><span class="code-line">    Content begin <span class="token string">"Hello World!"</span> <span class="token operator">/</span>\n<span class="token operator">&#x3C;</span><span class="token operator">></span><span class="token string">""</span> end<span class="token punctuation">.</span>
</span><span class="code-line">    <span class="token string">""</span>"<span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>multiLine<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// => Content begin "Hello World!" /\n&#x3C;>"" end.</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="字符串判空"><a aria-hidden="true" tabindex="-1" href="#字符串判空"><span class="icon icon-link"></span></a>字符串判空</h3><div class="wrap-body">
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<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> name<span class="token punctuation">;</span> <span class="token comment">//空引用</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> gender <span class="token operator">=</span> <span class="token string">""</span><span class="token punctuation">;</span> <span class="token comment">//空值</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 使用 string.IsNullOrEmpty(字符串) 方法，返回 bool 型</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token keyword">string</span><span class="token punctuation">.</span><span class="token function">IsNullOrEmpty</span><span class="token punctuation">(</span>name<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//输出 true</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token keyword">string</span><span class="token punctuation">.</span><span class="token function">IsNullOrEmpty</span><span class="token punctuation">(</span>gender<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 输出 true</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="字符串截取"><a aria-hidden="true" tabindex="-1" href="#字符串截取"><span class="icon icon-link"></span></a>字符串截取</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> Str <span class="token operator">=</span> <span class="token string">"字符串截取"</span><span class="token punctuation">;</span>
</span><span class="code-line">Str <span class="token operator">=</span> Str<span class="token punctuation">.</span><span class="token function">Substring</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>Str<span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">// 输出结果“串”，意为从第二个下标开始截取一位字符</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="字符串分割"><a aria-hidden="true" tabindex="-1" href="#字符串分割"><span class="icon icon-link"></span></a>字符串分割</h3><div class="wrap-body">
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<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> Name <span class="token operator">=</span> <span class="token string">"字A符A串A分A割"</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span><span class="token punctuation">[</span><span class="token punctuation">]</span></span> Names<span class="token operator">=</span>Name<span class="token punctuation">.</span><span class="token function">Split</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token constructor-invocation class-name"><span class="token keyword">char</span><span class="token punctuation">[</span><span class="token punctuation">]</span></span> <span class="token punctuation">{</span> <span class="token char">'A'</span> <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">// 会以A为媒介把字符串分成若干份</span>
</span><span class="code-line"><span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token class-name"><span class="token keyword">int</span></span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&#x3C;</span> Names<span class="token punctuation">.</span>Length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    Console<span class="token punctuation">.</span><span class="token function">Write</span><span class="token punctuation">(</span>Names<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="字符串替换"><a aria-hidden="true" tabindex="-1" href="#字符串替换"><span class="icon icon-link"></span></a>字符串替换</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> Rep <span class="token operator">=</span> <span class="token string">"字符1替换"</span><span class="token punctuation">;</span>
</span><span class="code-line">Rep <span class="token operator">=</span> Rep<span class="token punctuation">.</span><span class="token function">Replace</span><span class="token punctuation">(</span><span class="token string">"1"</span><span class="token punctuation">,</span> <span class="token string">"串"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>Rep<span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">// 会把字符中的 “1”替换成“串”</span>
</span></code></pre>
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="运算符和表达式"><a aria-hidden="true" tabindex="-1" href="#运算符和表达式"><span class="icon icon-link"></span></a>运算符和表达式</h2><div class="wrap-body">
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="逻辑运算"><a aria-hidden="true" tabindex="-1" href="#逻辑运算"><span class="icon icon-link"></span></a>逻辑运算</h3><div class="wrap-body">
<!--rehype:wrap-class=row-span-2-->
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">//或运算, 与运算, 非运算</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> A <span class="token operator">=</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> B <span class="token operator">=</span> <span class="token boolean">false</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> Or <span class="token operator">=</span> A <span class="token operator">||</span> B<span class="token punctuation">;</span> <span class="token comment">// = A | B</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> And <span class="token operator">=</span> A <span class="token operator">&#x26;&#x26;</span> B<span class="token punctuation">;</span> <span class="token comment">// = A &#x26; B</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> Not <span class="token operator">=</span> <span class="token operator">!</span>A<span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">// ||,&#x26;&#x26; 与 |,&#x26; 分别为逻辑运算和条件逻辑运算, 两者的区别在于, </span>
</span><span class="code-line"><span class="token comment">// 前者仅在必要时才会计算右侧的值, 后者始终计算右侧的值. 例如:</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> C <span class="token operator">=</span> <span class="token boolean">false</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> D <span class="token operator">=</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token return-type class-name"><span class="token keyword">bool</span></span> <span class="token function">CalcD</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
</span><span class="code-line">  D <span class="token operator">=</span> <span class="token operator">!</span>D<span class="token punctuation">;</span>
</span><span class="code-line">  <span class="token keyword">return</span> D<span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> E <span class="token operator">=</span> C <span class="token operator">&#x26;&#x26;</span> <span class="token function">CalcD</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// C: false, D: false, E: false</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> F <span class="token operator">=</span> C <span class="token operator">&#x26;</span> <span class="token function">CalcD</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// C:false, D: true, F: false</span>
</span><span class="code-line"><span class="token comment">// 两种运算方法稍有不同, 计算结果始终相同, 但第二种可能造成其他影响.</span>
</span><span class="code-line"><span class="token comment">//异或运算</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> Xor <span class="token operator">=</span> A <span class="token operator">^</span> B<span class="token punctuation">;</span>
</span></code></pre>
<p>C# 中的逻辑运算支持可空布尔类型运算. 注意条件逻辑运算不支持可空布尔类型.</p>





















































































<table class="show-header"><thead><tr><th align="left">x</th><th>y</th><th>x &#x26; y</th><th>x | y</th><th>x ^ y</th><th>! x</th></tr></thead><tbody><tr><td align="left"><code>true</code></td><td><code>true</code></td><td><code>true</code></td><td><code>true</code></td><td>false</td><td>false</td></tr><tr><td align="left"><code>true</code></td><td>false</td><td>false</td><td><code>true</code></td><td><code>true</code></td><td>false</td></tr><tr><td align="left"><code>true</code></td><td><pur>null</pur></td><td><pur>null</pur></td><td><code>true</code></td><td><pur>null</pur></td><td>false</td></tr><tr><td align="left">false</td><td><code>true</code></td><td>false</td><td><code>true</code></td><td><code>true</code></td><td><code>true</code></td></tr><tr><td align="left">false</td><td>false</td><td>false</td><td>false</td><td>false</td><td><code>true</code></td></tr><tr><td align="left">false</td><td><pur>null</pur></td><td>false</td><td><pur>null</pur></td><td><pur>null</pur></td><td><code>true</code></td></tr><tr><td align="left"><pur>null</pur></td><td><code>true</code></td><td><pur>null</pur></td><td><code>true</code></td><td><pur>null</pur></td><td><pur>null</pur></td></tr><tr><td align="left"><pur>null</pur></td><td>false</td><td>false</td><td><pur>null</pur></td><td><pur>null</pur></td><td><pur>null</pur></td></tr><tr><td align="left"><pur>null</pur></td><td><pur>null</pur></td><td><pur>null</pur></td><td><pur>null</pur></td><td><pur>null</pur></td><td><pur>null</pur></td></tr></tbody></table>
<!--rehype:className=show-header-->
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="关系运算符"><a aria-hidden="true" tabindex="-1" href="#关系运算符"><span class="icon icon-link"></span></a>关系运算符</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-2-->
<p>C# 支持下表中的所有关系运算符。假设变量 A 的值为 1，变量 B 的值为 2，则：</p>








































<table class="show-header"><thead><tr><th align="left">运算符</th><th>描述</th><th>实例</th></tr></thead><tbody><tr><td align="left">==</td><td>检查两个操作数的值是否相等，如果相等则条件为真。</td><td>(A == B) 不为真。</td></tr><tr><td align="left">!=</td><td>检查两个操作数的值是否相等，如果不相等则条件为真。</td><td>(A != B) 为真。</td></tr><tr><td align="left">></td><td>检查左操作数的值是否大于右操作数的值，如果是则条件为真。</td><td>(A > B) 不为真。</td></tr><tr><td align="left">&#x3C;</td><td>检查左操作数的值是否小于右操作数的值，如果是则条件为真。</td><td>(A &#x3C; B) 为真。</td></tr><tr><td align="left">>=</td><td>检查左操作数的值是否大于或等于右操作数的值，如果是则条件为真。</td><td>(A >= B) 不为真。</td></tr><tr><td align="left">&#x3C;=</td><td>检查左操作数的值是否小于或等于右操作数的值，如果是则条件为真。</td><td>(A &#x3C;= B) 为真。</td></tr></tbody></table>
<!--rehype:className=show-header-->
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="算术运算符"><a aria-hidden="true" tabindex="-1" href="#算术运算符"><span class="icon icon-link"></span></a>算术运算符</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-2-->
<p>C# 支持下表中的所有算术运算符。假设变量 A 的值为 10，变量 B 的值为 20，则：</p>













































<table class="show-header"><thead><tr><th align="left">运算符</th><th>描述</th><th>实例</th></tr></thead><tbody><tr><td align="left">+</td><td>把两个操作数相加</td><td>A + B 将得到 30</td></tr><tr><td align="left">-</td><td>从第一个操作数中减去第二个操作数</td><td>A - B 将得到 -10</td></tr><tr><td align="left">*</td><td>把两个操作数相乘</td><td>A * B 将得到 200</td></tr><tr><td align="left">/</td><td>分子除以分母</td><td>B / A 将得到 2</td></tr><tr><td align="left">%</td><td>取模运算符，整除后的余数</td><td>B % A 将得到 0</td></tr><tr><td align="left">++</td><td>自增运算符，整数值增加 1</td><td>A++ 将得到 11</td></tr><tr><td align="left">--</td><td>自减运算符，整数值减少 1</td><td>A-- 将得到 9</td></tr></tbody></table>
<!--rehype:className=show-header-->
</div></div></div><div class="wrap h3body-not-exist col-span-2 row-span-3"><div class="wrap-header h3wrap"><h3 id="运算符优先级"><a aria-hidden="true" tabindex="-1" href="#运算符优先级"><span class="icon icon-link"></span></a>运算符优先级</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-2 row-span-3-->
<p>下表将按运算符优先级从高到低列出各个运算符，具有较高优先级的运算符出现在表格的上面，具有较低优先级的运算符出现在表格的下面。在表达式中，较高优先级的运算符会优先被计算。</p>





















































































<table class="show-header"><thead><tr><th align="left">类别</th><th>运算符</th><th>结合性</th></tr></thead><tbody><tr><td align="left">后缀</td><td>() [] -> . ++ - -</td><td>从左到右</td></tr><tr><td align="left">一元</td><td>+ - ! ~ ++ - - (type)* &#x26; sizeof</td><td>从右到左</td></tr><tr><td align="left">乘除</td><td>* / %</td><td>从左到右</td></tr><tr><td align="left">加减</td><td>+ -</td><td>从左到右</td></tr><tr><td align="left">移位</td><td>&#x3C;&#x3C; >></td><td>从左到右</td></tr><tr><td align="left">关系</td><td>&#x3C; &#x3C;= > >=</td><td>从左到右</td></tr><tr><td align="left">相等</td><td>== !=</td><td>从左到右</td></tr><tr><td align="left">位与 AND</td><td>&#x26;</td><td>从左到右</td></tr><tr><td align="left">位异或 XOR</td><td>^</td><td>从左到右</td></tr><tr><td align="left">位或 OR</td><td>|</td><td>从左到右</td></tr><tr><td align="left">逻辑与 AND</td><td>&#x26;&#x26;</td><td>从左到右</td></tr><tr><td align="left">逻辑或 OR</td><td>||</td><td>从左到右</td></tr><tr><td align="left">条件</td><td>?:</td><td>从右到左</td></tr><tr><td align="left">赋值</td><td>= += -= *= /= %=>>= &#x3C;&#x3C;= &#x26;= ^= |=</td><td>从右到左</td></tr><tr><td align="left">逗号</td><td>,</td><td>从左到右</td></tr></tbody></table>
<!--rehype:className=show-header-->
<p>运算符的优先级确定表达式中项的组合。这会影响到一个表达式如何计算。某些运算符比其他运算符有更高的优先级，例如，乘除运算符具有比加减运算符更高的优先级。</p>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="逻辑非运算符"><a aria-hidden="true" tabindex="-1" href="#逻辑非运算符"><span class="icon icon-link"></span></a>逻辑非运算符</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> passed <span class="token operator">=</span> <span class="token boolean">false</span><span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token operator">!</span>passed<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 输出: True</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token operator">!</span><span class="token boolean">true</span><span class="token punctuation">)</span><span class="token punctuation">;</span>   <span class="token comment">// 输出: False</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="逻辑与运算符-"><a aria-hidden="true" tabindex="-1" href="#逻辑与运算符-"><span class="icon icon-link"></span></a>逻辑“与”运算符 &#x26;</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token return-type class-name"><span class="token keyword">bool</span></span> <span class="token function">SecondOperand</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token string">"计算第二个操作数"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">    <span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> a <span class="token operator">=</span> <span class="token boolean">false</span> <span class="token operator">&#x26;</span> <span class="token function">SecondOperand</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>a<span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">// 输出:</span>
</span><span class="code-line"><span class="token comment">// 计算第二个操作数</span>
</span><span class="code-line"><span class="token comment">// False</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> b <span class="token operator">=</span> <span class="token boolean">true</span> <span class="token operator">&#x26;</span> <span class="token function">SecondOperand</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>b<span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">// 输出:</span>
</span><span class="code-line"><span class="token comment">// 计算第二个操作数</span>
</span><span class="code-line"><span class="token comment">// True</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="逻辑异或运算符-"><a aria-hidden="true" tabindex="-1" href="#逻辑异或运算符-"><span class="icon icon-link"></span></a>逻辑异或运算符 ^</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token boolean">true</span> <span class="token operator">^</span> <span class="token boolean">true</span><span class="token punctuation">)</span><span class="token punctuation">;</span>  <span class="token comment">// 输出: False</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token boolean">true</span> <span class="token operator">^</span> <span class="token boolean">false</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 输出: True</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token boolean">false</span> <span class="token operator">^</span> <span class="token boolean">true</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 输出: True</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token boolean">false</span> <span class="token operator">^</span> <span class="token boolean">false</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">// 输出: False</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="逻辑或运算符-"><a aria-hidden="true" tabindex="-1" href="#逻辑或运算符-"><span class="icon icon-link"></span></a>逻辑或运算符 |</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token return-type class-name"><span class="token keyword">bool</span></span> <span class="token function">SecondOperand</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token string">"计算第二个操作数"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">    <span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> a <span class="token operator">=</span> <span class="token boolean">true</span> <span class="token operator">|</span> <span class="token function">SecondOperand</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>a<span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">// 输出:</span>
</span><span class="code-line"><span class="token comment">// 计算第二个操作数</span>
</span><span class="code-line"><span class="token comment">// True</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> b <span class="token operator">=</span> <span class="token boolean">false</span> <span class="token operator">|</span> <span class="token function">SecondOperand</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>b<span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">// 输出:</span>
</span><span class="code-line"><span class="token comment">// 计算第二个操作数</span>
</span><span class="code-line"><span class="token comment">// True</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="条件逻辑与运算符-"><a aria-hidden="true" tabindex="-1" href="#条件逻辑与运算符-"><span class="icon icon-link"></span></a>条件逻辑“与”运算符 &#x26;&#x26;</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token return-type class-name"><span class="token keyword">bool</span></span> <span class="token function">SecondOperand</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token string">"计算第二个操作数"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">    <span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> a <span class="token operator">=</span> <span class="token boolean">false</span> <span class="token operator">&#x26;&#x26;</span> <span class="token function">SecondOperand</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>a<span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">// 输出:</span>
</span><span class="code-line"><span class="token comment">// False</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> b <span class="token operator">=</span> <span class="token boolean">true</span> <span class="token operator">&#x26;&#x26;</span> <span class="token function">SecondOperand</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>b<span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">// 输出:</span>
</span><span class="code-line"><span class="token comment">// 计算第二个操作数</span>
</span><span class="code-line"><span class="token comment">// True</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="条件逻辑或运算符-"><a aria-hidden="true" tabindex="-1" href="#条件逻辑或运算符-"><span class="icon icon-link"></span></a>条件逻辑或运算符 ||</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token return-type class-name"><span class="token keyword">bool</span></span> <span class="token function">SecondOperand</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token string">"计算第二个操作数"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">    <span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> a <span class="token operator">=</span> <span class="token boolean">true</span> <span class="token operator">||</span> <span class="token function">SecondOperand</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>a<span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">// 输出:</span>
</span><span class="code-line"><span class="token comment">// True</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> b <span class="token operator">=</span> <span class="token boolean">false</span> <span class="token operator">||</span> <span class="token function">SecondOperand</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>b<span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">// 输出:</span>
</span><span class="code-line"><span class="token comment">// 计算第二个操作数</span>
</span><span class="code-line"><span class="token comment">// True</span>
</span></code></pre>
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="类"><a aria-hidden="true" tabindex="-1" href="#类"><span class="icon icon-link"></span></a>类</h2><div class="wrap-body">
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="成员变量"><a aria-hidden="true" tabindex="-1" href="#成员变量"><span class="icon icon-link"></span></a>成员变量</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">MyClass</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token comment">// 私有变量</span>
</span><span class="code-line">    <span class="token keyword">private</span> <span class="token class-name"><span class="token keyword">int</span></span> myVariable<span class="token punctuation">;</span>
</span><span class="code-line">    <span class="token comment">// 公有属性</span>
</span><span class="code-line">    <span class="token keyword">public</span> <span class="token return-type class-name"><span class="token keyword">string</span></span> MyProperty <span class="token punctuation">{</span> <span class="token keyword">get</span><span class="token punctuation">;</span> <span class="token keyword">set</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="静态成员"><a aria-hidden="true" tabindex="-1" href="#静态成员"><span class="icon icon-link"></span></a>静态成员</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">MyClass</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token class-name"><span class="token keyword">int</span></span> StaticVariable <span class="token operator">=</span> <span class="token number">10</span><span class="token punctuation">;</span>
</span><span class="code-line">    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token return-type class-name"><span class="token keyword">void</span></span> <span class="token function">StaticMethod</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
</span><span class="code-line">    <span class="token punctuation">{</span>
</span><span class="code-line">        <span class="token comment">// 静态方法体</span>
</span><span class="code-line">    <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="构造函数"><a aria-hidden="true" tabindex="-1" href="#构造函数"><span class="icon icon-link"></span></a>构造函数</h3><div class="wrap-body">
<!--rehype:wrap-class=row-span-2-->
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">MyClass</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token comment">// 默认构造函数</span>
</span><span class="code-line">    <span class="token keyword">public</span> <span class="token function">MyClass</span><span class="token punctuation">(</span><span class="token punctuation">)</span> 
</span><span class="code-line">    <span class="token punctuation">{</span>
</span><span class="code-line">        <span class="token comment">// 初始化代码</span>
</span><span class="code-line">    <span class="token punctuation">}</span>
</span><span class="code-line">
</span><span class="code-line">    <span class="token comment">// 自定义构造函数</span>
</span><span class="code-line">    <span class="token keyword">public</span> <span class="token function">MyClass</span><span class="token punctuation">(</span><span class="token class-name"><span class="token keyword">int</span></span> <span class="token keyword">value</span><span class="token punctuation">)</span> 
</span><span class="code-line">    <span class="token punctuation">{</span>
</span><span class="code-line">        <span class="token comment">// 使用传入的值初始化</span>
</span><span class="code-line">    <span class="token punctuation">}</span>
</span><span class="code-line">
</span><span class="code-line">    <span class="token comment">// 析构函数</span>
</span><span class="code-line">    <span class="token operator">~</span><span class="token function">MyClass</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
</span><span class="code-line">        <span class="token comment">// Destructor body.</span>
</span><span class="code-line">    <span class="token punctuation">}</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="方法"><a aria-hidden="true" tabindex="-1" href="#方法"><span class="icon icon-link"></span></a>方法</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">MyClass</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token comment">// 无返回值方法</span>
</span><span class="code-line">    <span class="token keyword">public</span> <span class="token return-type class-name"><span class="token keyword">void</span></span> <span class="token function">MyMethod</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
</span><span class="code-line">    <span class="token punctuation">{</span>
</span><span class="code-line">        <span class="token comment">// 方法体</span>
</span><span class="code-line">    <span class="token punctuation">}</span>
</span><span class="code-line">    <span class="token comment">// 有返回值方法</span>
</span><span class="code-line">    <span class="token keyword">public</span> <span class="token return-type class-name"><span class="token keyword">int</span></span> <span class="token function">Add</span><span class="token punctuation">(</span><span class="token class-name"><span class="token keyword">int</span></span> a<span class="token punctuation">,</span> <span class="token class-name"><span class="token keyword">int</span></span> b<span class="token punctuation">)</span>
</span><span class="code-line">    <span class="token punctuation">{</span>
</span><span class="code-line">        <span class="token keyword">return</span> a <span class="token operator">+</span> b<span class="token punctuation">;</span>
</span><span class="code-line">    <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="属性"><a aria-hidden="true" tabindex="-1" href="#属性"><span class="icon icon-link"></span></a>属性</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">MyClass</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token keyword">private</span> <span class="token class-name"><span class="token keyword">string</span></span> myField<span class="token punctuation">;</span>
</span><span class="code-line">    
</span><span class="code-line">    <span class="token keyword">public</span> <span class="token return-type class-name"><span class="token keyword">string</span></span> MyProperty
</span><span class="code-line">    <span class="token punctuation">{</span>
</span><span class="code-line">        <span class="token keyword">get</span> <span class="token punctuation">{</span> <span class="token keyword">return</span> myField<span class="token punctuation">;</span> <span class="token punctuation">}</span>
</span><span class="code-line">        <span class="token keyword">set</span> <span class="token punctuation">{</span> myField <span class="token operator">=</span> <span class="token keyword">value</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
</span><span class="code-line">    <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="接口"><a aria-hidden="true" tabindex="-1" href="#接口"><span class="icon icon-link"></span></a>接口</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">public</span> <span class="token keyword">interface</span> <span class="token class-name">IMyInterface</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token return-type class-name"><span class="token keyword">void</span></span> <span class="token function">MyMethod</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 接口方法声明</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">MyClass</span> <span class="token punctuation">:</span> <span class="token type-list"><span class="token class-name">IMyInterface</span></span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token keyword">public</span> <span class="token return-type class-name"><span class="token keyword">void</span></span> <span class="token function">MyMethod</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token comment">// 实现接口方法</span>
</span><span class="code-line">    <span class="token punctuation">{</span>
</span><span class="code-line">        <span class="token comment">// 实现代码</span>
</span><span class="code-line">    <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist row-span-3"><div class="wrap-header h3wrap"><h3 id="继承"><a aria-hidden="true" tabindex="-1" href="#继承"><span class="icon icon-link"></span></a>继承</h3><div class="wrap-body">
<!--rehype:wrap-class=row-span-3-->
<p>注意</p>
<ul>
<li>在类定义中，只能有一个基类</li>
<li>继承了一个抽象类，必须实现所继承的所有抽象成员(除非派生类也是抽象的)</li>
<li>编译器不允许派生类的可访问性高于基类</li>
<li>内部类可以继承于一个公共基类，但公共类不能继承于一个内部基类</li>
</ul>
<p>因此，下述代码是合法的：</p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">MyBase</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token comment">// Class members.</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line"><span class="token keyword">internal</span> <span class="token keyword">class</span> <span class="token class-name">MyClass</span> <span class="token punctuation">:</span> <span class="token type-list"><span class="token class-name">MyBase</span></span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token comment">// Class members.</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
<p>下述代码不能编译:</p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">internal</span> <span class="token keyword">class</span> <span class="token class-name">MyBase</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token comment">// Class members.</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">MyClass</span> <span class="token punctuation">:</span> <span class="token type-list"><span class="token class-name">MyBase</span></span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token comment">// Class members.</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
<p>如果没有使用基类，被定义的类就只继承于基类 System.Object(它在 C# 中的别名是 object)。在继承层次结构中，所有类的根都是 <code>System.Object</code></p>
</div></div></div><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="访问修饰符-1"><a aria-hidden="true" tabindex="-1" href="#访问修饰符-1"><span class="icon icon-link"></span></a>访问修饰符</h3><div class="wrap-body">
<!--rehype:wrap-class=row-span-2-->

































<table class="style-list"><thead><tr><th align="left">:--</th><th align="left">:--</th></tr></thead><tbody><tr><td align="left"><code>public</code></td><td align="left">公有，可从任何位置访问</td></tr><tr><td align="left"><code>private</code></td><td align="left">私有，只能在当前类中访问</td></tr><tr><td align="left"><code>protected</code></td><td align="left">受保护，只能在当前类和派生类中访问</td></tr><tr><td align="left"><code>internal</code></td><td align="left">内部，只能在同一程序集中访问</td></tr><tr><td align="left"><code>protected internal</code></td><td align="left">受保护的内部，可以在同一程序集中的任何地方访问，以及派生类中</td></tr><tr><td align="left"><code>private protected</code></td><td align="left">私有保护，只能在同一程序集中的派生类中访问</td></tr></tbody></table>
<!--rehype:className=style-list-->
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="字段的特殊修饰符"><a aria-hidden="true" tabindex="-1" href="#字段的特殊修饰符"><span class="icon icon-link"></span></a>字段的特殊修饰符</h3><div class="wrap-body">





















<table class="left-align"><thead><tr><th>:--</th><th>:--</th></tr></thead><tbody><tr><td><code>readonly</code></td><td>表示这个字段只能在执行构造函数的过程中赋值，或由初始化赋值语句赋值</td></tr><tr><td><code>static</code></td><td>静态字段，必须通过类名来访问，例如：Class.staticField</td></tr><tr><td><code>const</code></td><td>常量字段，但同时也是静态字段，自带static</td></tr></tbody></table>
<!--rehype:className=left-align-->
</div></div></div><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="方法的特殊修饰符"><a aria-hidden="true" tabindex="-1" href="#方法的特殊修饰符"><span class="icon icon-link"></span></a>方法的特殊修饰符</h3><div class="wrap-body">
<!--rehype:wrap-class=row-span-2-->

































<table class="left-align"><thead><tr><th>:--</th><th>:--</th></tr></thead><tbody><tr><td><code>static</code></td><td>静态方法，只能通过类名来调用方法</td></tr><tr><td><code>virtual</code></td><td>方法可以被重写</td></tr><tr><td><code>abstract</code></td><td>抽象方法，只用于抽象类</td></tr><tr><td><code>override</code></td><td>方法重写了基类的一个方法（如果方法被重写，就必须使用该关键字）。</td></tr><tr><td><code>extern</code></td><td>方法定义放在其他地方，可以在项目外部提供方法的实际实现代码</td></tr><tr><td><code>sealed</code></td><td>如果使用了 <code>override</code> ，也可以使用 <code>sealed</code> 来指定在派生类中不能再对这个方法进行进一步的修改，即这个方法不能被派生类重写</td></tr></tbody></table>
<!--rehype:className=left-align-->
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="公共类"><a aria-hidden="true" tabindex="-1" href="#公共类"><span class="icon icon-link"></span></a>公共类</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">MyClass</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">  <span class="token range operator">..</span><span class="token punctuation">.</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
<p>添加 <code>public</code> 声明为公共类</p>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="私有类"><a aria-hidden="true" tabindex="-1" href="#私有类"><span class="icon icon-link"></span></a>私有类</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">private</span> <span class="token keyword">class</span> <span class="token class-name">MyClass</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">  <span class="token range operator">..</span><span class="token punctuation">.</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
<p>添加 <code>public</code> 声明为公共类</p>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="命名约定"><a aria-hidden="true" tabindex="-1" href="#命名约定"><span class="icon icon-link"></span></a>命名约定</h3><div class="wrap-body">
<ul>
<li>类名使用 PascalCase 格式</li>
<li>成员变量和方法名使用 camelCase 格式</li>
<li>公有成员和类型名应该使用有意义的名字</li>
</ul>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="默认情况默认情况即为内部类"><a aria-hidden="true" tabindex="-1" href="#默认情况默认情况即为内部类"><span class="icon icon-link"></span></a>默认情况(默认情况即为内部类)</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">class</span> <span class="token class-name">MyClass</span> 
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">  <span class="token range operator">..</span><span class="token punctuation">.</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line"><span class="token keyword">internal</span> <span class="token keyword">class</span> <span class="token class-name">MyCalss</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">  <span class="token range operator">..</span><span class="token punctuation">.</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
<p>上面两个类相同，声明为内部（<code>internal</code>）类，只能在当前项目中的代码才能访问它</p>
<hr>
<ul>
<li>抽象类与密封类为互斥关系</li>
<li>抽象类不能实例化，允许继承</li>
<li>可以有抽象成员，密封类不允许继承</li>
<li>都可以声明为公共类（public）和内部类（internal）</li>
</ul>
</div></div></div><div class="wrap h3body-exist"><div class="wrap-header h3wrap"><h3 id="抽象类与密封类"><a aria-hidden="true" tabindex="-1" href="#抽象类与密封类"><span class="icon icon-link"></span></a>抽象类与密封类</h3><div class="wrap-body">
<h4 id="抽象类abstract"><a aria-hidden="true" tabindex="-1" href="#抽象类abstract"><span class="icon icon-link"></span></a>抽象类（abstract）</h4>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">public</span> <span class="token keyword">abstract</span> <span class="token keyword">class</span> <span class="token class-name">MyClass</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">  <span class="token comment">// 普通公共字段</span>
</span><span class="code-line">  <span class="token keyword">public</span> <span class="token class-name"><span class="token keyword">string</span></span> id<span class="token punctuation">;</span>
</span><span class="code-line">  <span class="token comment">// 抽象字段</span>
</span><span class="code-line">  <span class="token keyword">public</span> <span class="token keyword">abstract</span> <span class="token return-type class-name"><span class="token keyword">string</span></span> Name <span class="token punctuation">{</span> <span class="token keyword">get</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
</span><span class="code-line">  <span class="token comment">// 常量字段</span>
</span><span class="code-line">  <span class="token keyword">public</span> <span class="token keyword">const</span> <span class="token class-name"><span class="token keyword">string</span></span> Description <span class="token operator">=</span> <span class="token string">"常量"</span><span class="token punctuation">;</span>
</span><span class="code-line">  <span class="token comment">// 静态字段</span>
</span><span class="code-line">  <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token class-name"><span class="token keyword">string</span></span> Order <span class="token operator">=</span> <span class="token string">"静态"</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
<h4 id="密封类sealed"><a aria-hidden="true" tabindex="-1" href="#密封类sealed"><span class="icon icon-link"></span></a>密封类（sealed</h4>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">public</span> <span class="token keyword">sealed</span> <span class="token keyword">class</span> <span class="token class-name">MyClass</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">  <span class="token range operator">..</span><span class="token punctuation">.</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="元组"><a aria-hidden="true" tabindex="-1" href="#元组"><span class="icon icon-link"></span></a>元组</h2><div class="wrap-body">
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="基本使用"><a aria-hidden="true" tabindex="-1" href="#基本使用"><span class="icon icon-link"></span></a>基本使用</h3><div class="wrap-body">
<p>不带名称的基本元组创建</p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token punctuation">(</span>
</span><span class="code-line">    <span class="token class-name"><span class="token keyword">int</span></span> item1<span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token class-name"><span class="token keyword">string</span></span> item2<span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token class-name"><span class="token keyword">bool</span></span> item3
</span><span class="code-line"><span class="token punctuation">)</span> tuple1 <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token string">"Hello"</span><span class="token punctuation">,</span> <span class="token boolean">true</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>
</span><span class="code-line">    <span class="token interpolation-string"><span class="token string">$"Item1: </span><span class="token interpolation"><span class="token punctuation">{</span><span class="token expression language-csharp">tuple1<span class="token punctuation">.</span>Item1</span><span class="token punctuation">}</span></span><span class="token string">, "</span></span> <span class="token operator">+</span>
</span><span class="code-line">    <span class="token interpolation-string"><span class="token string">$"Item2: </span><span class="token interpolation"><span class="token punctuation">{</span><span class="token expression language-csharp">tuple1<span class="token punctuation">.</span>Item2</span><span class="token punctuation">}</span></span><span class="token string">, "</span></span> <span class="token operator">+</span>
</span><span class="code-line">    <span class="token interpolation-string"><span class="token string">$"Item3: </span><span class="token interpolation"><span class="token punctuation">{</span><span class="token expression language-csharp">tuple1<span class="token punctuation">.</span>Item3</span><span class="token punctuation">}</span></span><span class="token string">"</span></span>
</span><span class="code-line"><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
<p>带名称的元组创建（C# 7.0及以上版本）</p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token punctuation">(</span>
</span><span class="code-line">    <span class="token class-name"><span class="token keyword">string</span></span> FirstName<span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token class-name"><span class="token keyword">string</span></span> LastName<span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token class-name"><span class="token keyword">int</span></span> Age
</span><span class="code-line"><span class="token punctuation">)</span> person <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token string">"Alice"</span><span class="token punctuation">,</span> <span class="token string">"Smith"</span><span class="token punctuation">,</span> <span class="token number">30</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>
</span><span class="code-line">    <span class="token interpolation-string"><span class="token string">$"First Name: </span><span class="token interpolation"><span class="token punctuation">{</span><span class="token expression language-csharp">person<span class="token punctuation">.</span>FirstName</span><span class="token punctuation">}</span></span><span class="token string">, "</span></span> <span class="token operator">+</span>
</span><span class="code-line">    <span class="token interpolation-string"><span class="token string">$"Last Name: </span><span class="token interpolation"><span class="token punctuation">{</span><span class="token expression language-csharp">person<span class="token punctuation">.</span>LastName</span><span class="token punctuation">}</span></span><span class="token string">, "</span></span> <span class="token operator">+</span>
</span><span class="code-line">    <span class="token interpolation-string"><span class="token string">$"Age: </span><span class="token interpolation"><span class="token punctuation">{</span><span class="token expression language-csharp">person<span class="token punctuation">.</span>Age</span><span class="token punctuation">}</span></span><span class="token string">"</span></span>
</span><span class="code-line"><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="方法调用与接收"><a aria-hidden="true" tabindex="-1" href="#方法调用与接收"><span class="icon icon-link"></span></a>方法调用与接收</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">public</span> <span class="token return-type class-name"><span class="token punctuation">(</span><span class="token keyword">int</span> Id<span class="token punctuation">,</span> <span class="token keyword">string</span> Name<span class="token punctuation">,</span> <span class="token keyword">double</span> Score<span class="token punctuation">)</span></span> <span class="token function">GetStudentInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token keyword">return</span> <span class="token punctuation">(</span><span class="token number">123</span><span class="token punctuation">,</span> <span class="token string">"John Doe"</span><span class="token punctuation">,</span> <span class="token number">95.5</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
<p>使用</p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token punctuation">(</span>
</span><span class="code-line">    <span class="token class-name"><span class="token keyword">var</span></span> id<span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token class-name"><span class="token keyword">var</span></span> name<span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token class-name"><span class="token keyword">var</span></span> score
</span><span class="code-line"><span class="token punctuation">)</span> <span class="token operator">=</span> <span class="token function">GetStudentInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span>
</span><span class="code-line">    <span class="token interpolation-string"><span class="token string">$"Id: </span><span class="token interpolation"><span class="token punctuation">{</span><span class="token expression language-csharp">id</span><span class="token punctuation">}</span></span><span class="token string">, "</span></span> <span class="token operator">+</span>
</span><span class="code-line">    <span class="token interpolation-string"><span class="token string">$"Name: </span><span class="token interpolation"><span class="token punctuation">{</span><span class="token expression language-csharp">name</span><span class="token punctuation">}</span></span><span class="token string">, "</span></span> <span class="token operator">+</span>
</span><span class="code-line">    <span class="token interpolation-string"><span class="token string">$"Score: </span><span class="token interpolation"><span class="token punctuation">{</span><span class="token expression language-csharp">score</span><span class="token punctuation">}</span></span><span class="token string">"</span></span>
</span><span class="code-line"><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="类中使用元组"><a aria-hidden="true" tabindex="-1" href="#类中使用元组"><span class="icon icon-link"></span></a>类中使用元组</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">Student</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token keyword">public</span> <span class="token return-type class-name"><span class="token keyword">int</span></span> Id <span class="token punctuation">{</span> <span class="token keyword">get</span><span class="token punctuation">;</span> <span class="token keyword">set</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
</span><span class="code-line">    <span class="token keyword">public</span> <span class="token return-type class-name"><span class="token keyword">string</span></span> Name <span class="token punctuation">{</span> <span class="token keyword">get</span><span class="token punctuation">;</span> <span class="token keyword">set</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
</span><span class="code-line">    <span class="token keyword">public</span> <span class="token return-type class-name"><span class="token keyword">double</span></span> GPA <span class="token punctuation">{</span> <span class="token keyword">get</span><span class="token punctuation">;</span> <span class="token keyword">set</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
</span><span class="code-line">
</span><span class="code-line">    <span class="token keyword">public</span> <span class="token return-type class-name"><span class="token keyword">void</span></span> <span class="token function">Deconstruct</span><span class="token punctuation">(</span><span class="token keyword">out</span> <span class="token class-name"><span class="token keyword">int</span></span> id<span class="token punctuation">,</span> <span class="token keyword">out</span> <span class="token class-name"><span class="token keyword">string</span></span> name<span class="token punctuation">,</span> <span class="token keyword">out</span> <span class="token class-name"><span class="token keyword">double</span></span> gpa<span class="token punctuation">)</span>
</span><span class="code-line">    <span class="token punctuation">{</span>
</span><span class="code-line">        id <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>Id<span class="token punctuation">;</span>
</span><span class="code-line">        name <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>Name<span class="token punctuation">;</span>
</span><span class="code-line">        gpa <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>GPA<span class="token punctuation">;</span>
</span><span class="code-line">    <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
<p>使用Deconstruct方法创建元组</p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name">Student</span> student <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    Id <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">,</span>
</span><span class="code-line">    Name <span class="token operator">=</span> <span class="token string">"Jane"</span><span class="token punctuation">,</span>
</span><span class="code-line">    GPA <span class="token operator">=</span> <span class="token number">3.8</span>
</span><span class="code-line"><span class="token punctuation">}</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token punctuation">(</span><span class="token class-name"><span class="token keyword">int</span></span> id<span class="token punctuation">,</span> <span class="token class-name"><span class="token keyword">string</span></span> name<span class="token punctuation">,</span> <span class="token class-name"><span class="token keyword">double</span></span> gpa<span class="token punctuation">)</span> <span class="token operator">=</span> student<span class="token punctuation">;</span>
</span><span class="code-line">Console<span class="token punctuation">.</span><span class="token function">WriteLine</span><span class="token punctuation">(</span><span class="token interpolation-string"><span class="token string">$"Student Id: </span><span class="token interpolation"><span class="token punctuation">{</span><span class="token expression language-csharp">id</span><span class="token punctuation">}</span></span><span class="token string">, Name: </span><span class="token interpolation"><span class="token punctuation">{</span><span class="token expression language-csharp">name</span><span class="token punctuation">}</span></span><span class="token string">, GPA: </span><span class="token interpolation"><span class="token punctuation">{</span><span class="token expression language-csharp">gpa</span><span class="token punctuation">}</span></span><span class="token string">"</span></span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="集合"><a aria-hidden="true" tabindex="-1" href="#集合"><span class="icon icon-link"></span></a>集合</h2><div class="wrap-body">
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist col-span-2 row-span-2"><div class="wrap-header h3wrap"><h3 id="c集合"><a aria-hidden="true" tabindex="-1" href="#c集合"><span class="icon icon-link"></span></a>c#集合</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-2 row-span-2-->





















































































































<table class="show-header"><thead><tr><th align="left">集合</th><th align="left">有序</th><th align="left">已排序</th><th align="left">线程安全</th><th align="left">允许空值</th></tr></thead><tbody><tr><td align="left"><a href="https://docs.microsoft.com/dotnet/api/system.collections.generic.list-1">List</a></td><td align="left">Y</td><td align="left"><em>N</em></td><td align="left"><em>N</em></td><td align="left">是</td></tr><tr><td align="left"><a href="https://docs.microsoft.com/dotnet/api/system.collections.arraylist">ArrayList</a> (非泛型)</td><td align="left">Y</td><td align="left"><em>N</em></td><td align="left"><em>N</em></td><td align="left">是</td></tr><tr><td align="left"><a href="https://docs.microsoft.com/dotnet/api/system.collections.vector">Vector</a> (非泛型)</td><td align="left"><em>N</em></td><td align="left"><em>N</em></td><td align="left">Y</td><td align="left">是</td></tr><tr><td align="left"><a href="https://docs.microsoft.com/dotnet/api/system.collections.generic.linkedlist-1">LinkedList</a></td><td align="left">Y</td><td align="left"><em>N</em></td><td align="left"><em>N</em></td><td align="left">是</td></tr><tr><td align="left"><a href="https://docs.microsoft.com/dotnet/api/system.collections.concurrent.concurrentbag-1">ConcurrentBag</a></td><td align="left"><em>N</em></td><td align="left"><em>N</em></td><td align="left">Y</td><td align="left">是</td></tr><tr><td align="left"><a href="https://docs.microsoft.com/dotnet/api/system.collections.generic.hashset-1">HashSet</a></td><td align="left"><em>N</em></td><td align="left"><em>N</em></td><td align="left"><em>N</em></td><td align="left">是</td></tr><tr><td align="left"><a href="https://docs.microsoft.com/dotnet/api/system.collections.generic.sortedset-1">SortedSet</a></td><td align="left"><em>N</em></td><td align="left">Y</td><td align="left"><em>N</em></td><td align="left">是</td></tr><tr><td align="left"><a href="https://docs.microsoft.com/dotnet/api/system.collections.concurrent.concurrentdictionary-2">ConcurrentDictionary</a></td><td align="left">Y</td><td align="left"><em>N</em></td><td align="left">Y</td><td align="left">是</td></tr><tr><td align="left"><a href="https://docs.microsoft.com/dotnet/api/system.collections.generic.dictionary-2">Dictionary</a></td><td align="left"><em>N</em></td><td align="left"><em>N</em></td><td align="left"><em>N</em></td><td align="left">是</td></tr><tr><td align="left"><a href="https://docs.microsoft.com/dotnet/api/system.collections.generic.sorteddictionary-2">SortedDictionary</a></td><td align="left">Y</td><td align="left">Y</td><td align="left"><em>N</em></td><td align="left">是</td></tr><tr><td align="left"><a href="https://docs.microsoft.com/dotnet/api/system.collections.generic.stack-1">Stack</a></td><td align="left"><em>N</em></td><td align="left"><em>N</em></td><td align="left"><em>N</em></td><td align="left">是</td></tr><tr><td align="left"><a href="https://docs.microsoft.com/dotnet/api/system.collections.generic.queue-1">Queue</a></td><td align="left"><em>N</em></td><td align="left"><em>N</em></td><td align="left"><em>N</em></td><td align="left">是</td></tr><tr><td align="left"><a href="https://docs.microsoft.com/dotnet/api/system.collections.concurrent.concurrentqueue-1">ConcurrentQueue</a></td><td align="left"><em>N</em></td><td align="left"><em>N</em></td><td align="left">Y</td><td align="left">是</td></tr><tr><td align="left"><a href="https://docs.microsoft.com/dotnet/api/system.collections.concurrent.concurrentstack-1">ConcurrentStack</a></td><td align="left"><em>N</em></td><td align="left"><em>N</em></td><td align="left">Y</td><td align="left">是</td></tr><tr><td align="left"><a href="https://learn.microsoft.com/zh-cn/dotnet/api/system.collections.hashtable?view=net-6.0">HashTable</a></td><td align="left">N</td><td align="left">Y</td><td align="left">Y</td><td align="left">否</td></tr></tbody></table>
<!--rehype:className=show-header-->
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="list"><a aria-hidden="true" tabindex="-1" href="#list"><span class="icon icon-link"></span></a>List</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 创建一个整数类型的List</span>
</span><span class="code-line"><span class="token class-name">List<span class="token punctuation">&#x3C;</span><span class="token keyword">int</span><span class="token punctuation">></span></span> numbers <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">List<span class="token punctuation">&#x3C;</span><span class="token keyword">int</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 增加（Add）</span>
</span><span class="code-line">numbers<span class="token punctuation">.</span><span class="token function">Add</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">numbers<span class="token punctuation">.</span><span class="token function">Add</span><span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">//增加30，40两个元素</span>
</span><span class="code-line">numbers<span class="token punctuation">.</span><span class="token function">AddRange</span><span class="token punctuation">(</span><span class="token keyword">new</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span> <span class="token number">30</span><span class="token punctuation">,</span> <span class="token number">40</span> <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 删除（Remove）</span>
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span>numbers<span class="token punctuation">.</span><span class="token function">Contains</span><span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    numbers<span class="token punctuation">.</span><span class="token function">Remove</span><span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 修改（更改特定索引处的元素）</span>
</span><span class="code-line">numbers<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">50</span><span class="token punctuation">;</span> <span class="token comment">// 直接替换元素</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 查询（Find/Contains）</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> isPresent <span class="token operator">=</span> numbers<span class="token punctuation">.</span><span class="token function">Contains</span><span class="token punctuation">(</span><span class="token number">50</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 查找索引</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">int</span></span> index <span class="token operator">=</span> numbers<span class="token punctuation">.</span><span class="token function">IndexOf</span><span class="token punctuation">(</span><span class="token number">40</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span>index <span class="token operator">!=</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    numbers<span class="token punctuation">[</span>index<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">45</span><span class="token punctuation">;</span> <span class="token comment">// 修改找到的元素</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="hashset"><a aria-hidden="true" tabindex="-1" href="#hashset"><span class="icon icon-link"></span></a>HashSet</h3><div class="wrap-body">
<pre class="wrap-text"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 创建一个字符串类型的HashSet</span>
</span><span class="code-line"><span class="token class-name">HashSet<span class="token punctuation">&#x3C;</span><span class="token keyword">string</span><span class="token punctuation">></span></span> words <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">HashSet<span class="token punctuation">&#x3C;</span><span class="token keyword">string</span><span class="token punctuation">></span></span> <span class="token punctuation">{</span> <span class="token string">"apple"</span><span class="token punctuation">,</span> <span class="token string">"banana"</span> <span class="token punctuation">}</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 增加（Add）</span>
</span><span class="code-line">words<span class="token punctuation">.</span><span class="token function">Add</span><span class="token punctuation">(</span><span class="token string">"cherry"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 返回 false，因为"apple"已存在</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> wasAdded <span class="token operator">=</span> words<span class="token punctuation">.</span><span class="token function">Add</span><span class="token punctuation">(</span><span class="token string">"apple"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> 
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 删除（Remove）</span>
</span><span class="code-line">words<span class="token punctuation">.</span><span class="token function">Remove</span><span class="token punctuation">(</span><span class="token string">"banana"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 修改 - HashSet不允许直接修改元素</span>
</span><span class="code-line"><span class="token comment">// 需删除后重新添加</span>
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span>words<span class="token punctuation">.</span><span class="token function">Contains</span><span class="token punctuation">(</span><span class="token string">"cherry"</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    words<span class="token punctuation">.</span><span class="token function">Remove</span><span class="token punctuation">(</span><span class="token string">"cherry"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">    words<span class="token punctuation">.</span><span class="token function">Add</span><span class="token punctuation">(</span><span class="token string">"cherries"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 查询（Contains）</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> containsCherries <span class="token operator">=</span> words<span class="token punctuation">.</span><span class="token function">Contains</span><span class="token punctuation">(</span><span class="token string">"cherries"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
<!--rehype:className=wrap-text-->
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="concurrentbag"><a aria-hidden="true" tabindex="-1" href="#concurrentbag"><span class="icon icon-link"></span></a>ConcurrentBag</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-2-->
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 创建一个并发安全的整数集合</span>
</span><span class="code-line"><span class="token class-name">ConcurrentBag<span class="token punctuation">&#x3C;</span><span class="token keyword">int</span><span class="token punctuation">></span></span> concurrentNumbers <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">ConcurrentBag<span class="token punctuation">&#x3C;</span><span class="token keyword">int</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 增加（Add）</span>
</span><span class="code-line">concurrentNumbers<span class="token punctuation">.</span><span class="token function">Add</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">concurrentNumbers<span class="token punctuation">.</span><span class="token function">Add</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 删除（由于ConcurrentBag没有直接的Remove方法，只能通过迭代并尝试移除）</span>
</span><span class="code-line"><span class="token keyword">foreach</span> <span class="token punctuation">(</span><span class="token class-name"><span class="token keyword">var</span></span> number <span class="token keyword">in</span> concurrentNumbers<span class="token punctuation">.</span><span class="token function">ToArray</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    concurrentNumbers<span class="token punctuation">.</span><span class="token function">TryTake</span><span class="token punctuation">(</span><span class="token keyword">out</span> _number<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 并发安全地移除一个元素</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
<p>修改（无法直接修改，同样需先移除再添加，但由于并发特性，不能保证一定能修改目标元素）。
在并发环境下尤其复杂，此处省略示例</p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 查询（Contains）</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> hasOne <span class="token operator">=</span> concurrentNumbers<span class="token punctuation">.</span><span class="token function">Contains</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="stack"><a aria-hidden="true" tabindex="-1" href="#stack"><span class="icon icon-link"></span></a>Stack</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 创建一个整数栈</span>
</span><span class="code-line"><span class="token class-name">Stack<span class="token punctuation">&#x3C;</span><span class="token keyword">int</span><span class="token punctuation">></span></span> stack <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Stack<span class="token punctuation">&#x3C;</span><span class="token keyword">int</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">stack<span class="token punctuation">.</span><span class="token function">Push</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">stack<span class="token punctuation">.</span><span class="token function">Push</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 增加（Push）</span>
</span><span class="code-line">stack<span class="token punctuation">.</span><span class="token function">Push</span><span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 删除（Pop）并返回栈顶元素</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">int</span></span> topNumber <span class="token operator">=</span> stack<span class="token punctuation">.</span><span class="token function">Pop</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 修改（Stack不支持直接修改元素，需先Pop再Push）</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">int</span></span> poppedValue <span class="token operator">=</span> stack<span class="token punctuation">.</span><span class="token function">Pop</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token comment">// 替换刚弹出的值</span>
</span><span class="code-line">stack<span class="token punctuation">.</span><span class="token function">Push</span><span class="token punctuation">(</span>poppedValue <span class="token operator">*</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span> 
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 查询（Peek / Contains） 但不移除栈顶元素</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">int</span></span> peekedValue <span class="token operator">=</span> stack<span class="token punctuation">.</span><span class="token function">Peek</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> hasTwo <span class="token operator">=</span> stack<span class="token punctuation">.</span><span class="token function">Contains</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="dictionary"><a aria-hidden="true" tabindex="-1" href="#dictionary"><span class="icon icon-link"></span></a>Dictionary</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-2-->
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 创建一个键值对字典</span>
</span><span class="code-line"><span class="token class-name">Dictionary<span class="token punctuation">&#x3C;</span><span class="token keyword">string</span><span class="token punctuation">,</span> <span class="token keyword">int</span><span class="token punctuation">></span></span> scores <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Dictionary<span class="token punctuation">&#x3C;</span><span class="token keyword">string</span><span class="token punctuation">,</span> <span class="token keyword">int</span><span class="token punctuation">></span></span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token punctuation">{</span> <span class="token string">"Alice"</span><span class="token punctuation">,</span> <span class="token number">85</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token punctuation">{</span> <span class="token string">"Bob"</span><span class="token punctuation">,</span> <span class="token number">90</span> <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 增加（Add）</span>
</span><span class="code-line">scores<span class="token punctuation">.</span><span class="token function">Add</span><span class="token punctuation">(</span><span class="token string">"Charlie"</span><span class="token punctuation">,</span> <span class="token number">88</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 删除（Remove）</span>
</span><span class="code-line">scores<span class="token punctuation">.</span><span class="token function">Remove</span><span class="token punctuation">(</span><span class="token string">"Bob"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 修改（Update）</span>
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span>scores<span class="token punctuation">.</span><span class="token function">ContainsKey</span><span class="token punctuation">(</span><span class="token string">"Alice"</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    scores<span class="token punctuation">[</span><span class="token string">"Alice"</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">90</span><span class="token punctuation">;</span> <span class="token comment">// 直接替换值</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 查询（ContainsKey / GetValueOrDefault）</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> aliceExists <span class="token operator">=</span> scores<span class="token punctuation">.</span><span class="token function">ContainsKey</span><span class="token punctuation">(</span><span class="token string">"Alice"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">int</span></span> charlieScore <span class="token operator">=</span> scores<span class="token punctuation">.</span><span class="token function">GetValueOrDefault</span><span class="token punctuation">(</span><span class="token string">"Charlie"</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="hashtable"><a aria-hidden="true" tabindex="-1" href="#hashtable"><span class="icon icon-link"></span></a>Hashtable</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 创建一个哈希表</span>
</span><span class="code-line"><span class="token class-name">Hashtable</span> hashTable <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Hashtable</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">hashTable<span class="token punctuation">.</span><span class="token function">Add</span><span class="token punctuation">(</span><span class="token string">"key1"</span><span class="token punctuation">,</span> <span class="token string">"value1"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">hashTable<span class="token punctuation">.</span><span class="token function">Add</span><span class="token punctuation">(</span><span class="token string">"key2"</span><span class="token punctuation">,</span> <span class="token string">"value2"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 增加（Add）</span>
</span><span class="code-line">hashTable<span class="token punctuation">.</span><span class="token function">Add</span><span class="token punctuation">(</span><span class="token string">"key3"</span><span class="token punctuation">,</span> <span class="token string">"value3"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 删除（Remove）</span>
</span><span class="code-line">hashTable<span class="token punctuation">.</span><span class="token function">Remove</span><span class="token punctuation">(</span><span class="token string">"key1"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 修改（Replace）</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">object</span></span> oldValue<span class="token punctuation">;</span>
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span>hashTable<span class="token punctuation">.</span><span class="token function">ContainsKey</span><span class="token punctuation">(</span><span class="token string">"key2"</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    oldValue <span class="token operator">=</span> hashTable<span class="token punctuation">[</span><span class="token string">"key2"</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
</span><span class="code-line">    hashTable<span class="token punctuation">[</span><span class="token string">"key2"</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token string">"new_value2"</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 查询（Contains / GetValue）</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">bool</span></span> hasKey2 <span class="token operator">=</span> hashTable<span class="token punctuation">.</span><span class="token function">ContainsKey</span><span class="token punctuation">(</span><span class="token string">"key2"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> valueOfKey2 <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token keyword">string</span><span class="token punctuation">)</span>hashTable<span class="token punctuation">[</span><span class="token string">"key2"</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="linq"><a aria-hidden="true" tabindex="-1" href="#linq"><span class="icon icon-link"></span></a>LINQ</h2><div class="wrap-body">
<blockquote>
<p>C#语言中的LINQ（Language-Integrated Query）是一种强大的查询语言，它提供了一种统一的编程模型，使得数据查询变得更加直观和简洁。</p>
</blockquote>
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist col-span-3"><div class="wrap-header h3wrap"><h3 id="from"><a aria-hidden="true" tabindex="-1" href="#from"><span class="icon icon-link"></span></a>FROM</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-3-->
<blockquote>
<p>任何数据源，包括对象集合、数据库、XML等。</p>
</blockquote>
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 style="background:#e91e63;" id="where"><a aria-hidden="true" tabindex="-1" href="#where"><span class="icon icon-link"></span></a>WHERE</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-2&style=background:#e91e63;-->
<blockquote>
<p>条件查询</p>
</blockquote>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 示例数据源</span>
</span><span class="code-line"><span class="token class-name">List<span class="token punctuation">&#x3C;</span>Student<span class="token punctuation">></span></span> students <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">List<span class="token punctuation">&#x3C;</span>Student<span class="token punctuation">></span></span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Alice"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">25</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"A"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Bob"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">30</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"B"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Barry"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">35</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"C"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Charlie"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">22</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"A"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"David"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">21</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"C"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Damon"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">28</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"B"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Echo"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">18</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"C"</span> <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 使用WHERE筛选出成绩为A的学生</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> result1 <span class="token operator">=</span> students<span class="token punctuation">.</span><span class="token function">Where</span><span class="token punctuation">(</span>student <span class="token operator">=></span> student<span class="token punctuation">.</span>Grade <span class="token operator">=</span> <span class="token string">"A"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 使用WHERE筛选出年龄大于20的学生</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> result2 <span class="token operator">=</span> students<span class="token punctuation">.</span><span class="token function">Where</span><span class="token punctuation">(</span>student <span class="token operator">=></span> student<span class="token punctuation">.</span>Age <span class="token operator">></span> <span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 使用WHERE筛选出名字包含'D'的学生</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> result3 <span class="token operator">=</span> students<span class="token punctuation">.</span><span class="token function">Where</span><span class="token punctuation">(</span>student <span class="token operator">=></span> student<span class="token punctuation">.</span>Name<span class="token punctuation">.</span><span class="token function">Contains</span><span class="token punctuation">(</span><span class="token string">"D"</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 使用WHERE筛选出名字为'Bob'和'Echo'的学生</span>
</span><span class="code-line"><span class="token class-name">List<span class="token punctuation">&#x3C;</span><span class="token keyword">string</span><span class="token punctuation">></span></span> nameList <span class="token operator">=</span> <span class="token keyword">new</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token string">"Bob"</span><span class="token punctuation">,</span> <span class="token string">"Echo"</span> <span class="token punctuation">}</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> result4 <span class="token operator">=</span> students<span class="token punctuation">.</span><span class="token function">Where</span><span class="token punctuation">(</span>student <span class="token operator">=></span> nameList<span class="token punctuation">.</span><span class="token function">Contains</span><span class="token punctuation">(</span>student<span class="token punctuation">.</span>Name<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="groupby"><a aria-hidden="true" tabindex="-1" href="#groupby"><span class="icon icon-link"></span></a>GROUPBY</h3><div class="wrap-body">
<blockquote>
<p>分组查询</p>
</blockquote>
<pre class="wrap-text"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 示例数据源</span>
</span><span class="code-line"><span class="token class-name">List<span class="token punctuation">&#x3C;</span>Student<span class="token punctuation">></span></span> students <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">List<span class="token punctuation">&#x3C;</span>Student<span class="token punctuation">></span></span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Alice"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">25</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"A"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Bob"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">30</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"B"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Barry"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">35</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"C"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Charlie"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">22</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"A"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"David"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">21</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"C"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Damon"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">28</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"B"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Echo"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">18</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"C"</span> <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 使用GROUP BY按成绩进行分组查询</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> groupedByGrade <span class="token operator">=</span> students<span class="token punctuation">.</span><span class="token function">GroupBy</span><span class="token punctuation">(</span>student <span class="token operator">=></span> student<span class="token punctuation">.</span>Grade<span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
<!--rehype:className=wrap-text-->
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 style="background:#e91e63;" id="select"><a aria-hidden="true" tabindex="-1" href="#select"><span class="icon icon-link"></span></a>SELECT</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-2&style=background:#e91e63;-->
<blockquote>
<p>结果查询</p>
</blockquote>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 示例数据源</span>
</span><span class="code-line"><span class="token class-name">List<span class="token punctuation">&#x3C;</span>Student<span class="token punctuation">></span></span> students <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">List<span class="token punctuation">&#x3C;</span>Student<span class="token punctuation">></span></span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Alice"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">25</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"A"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Bob"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">30</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"B"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Barry"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">35</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"C"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Charlie"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">22</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"A"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"David"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">21</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"C"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Damon"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">28</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"B"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Echo"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">18</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"C"</span> <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 使用SELECT创建一个新的匿名类，并输出为集合，一般配合Where使用</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> result1 <span class="token operator">=</span> students<span class="token punctuation">.</span><span class="token function">Select</span><span class="token punctuation">(</span>student <span class="token operator">=></span> 
</span><span class="code-line">  <span class="token keyword">new</span> 
</span><span class="code-line">    <span class="token punctuation">{</span>
</span><span class="code-line">      student<span class="token punctuation">.</span>Name<span class="token punctuation">,</span>
</span><span class="code-line">        student<span class="token punctuation">.</span>Age
</span><span class="code-line">    <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 使用SELECT创建一个新的指定类，并输出为集合</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> result2 <span class="token operator">=</span> students<span class="token punctuation">.</span><span class="token function">Select</span><span class="token punctuation">(</span>student <span class="token operator">=></span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">StudentDto</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
</span><span class="code-line">    <span class="token punctuation">{</span>
</span><span class="code-line">        StudentName <span class="token operator">=</span> student<span class="token punctuation">.</span>Name<span class="token punctuation">,</span>
</span><span class="code-line">        StudentAge <span class="token operator">=</span> student<span class="token punctuation">.</span>Age
</span><span class="code-line">    <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="orderby"><a aria-hidden="true" tabindex="-1" href="#orderby"><span class="icon icon-link"></span></a>ORDERBY</h3><div class="wrap-body">
<blockquote>
<p>排序</p>
</blockquote>
<pre class="wrap-text"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 示例数据源</span>
</span><span class="code-line"><span class="token class-name">List<span class="token punctuation">&#x3C;</span>Student<span class="token punctuation">></span></span> students <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">List<span class="token punctuation">&#x3C;</span>Student<span class="token punctuation">></span></span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Alice"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">25</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"A"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Bob"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">30</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"B"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Barry"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">35</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"C"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Charlie"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">22</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"A"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"David"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">21</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"C"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Damon"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">28</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"B"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Echo"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">18</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"C"</span> <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 使用LINQ的OrderBy进行排序</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> result1 <span class="token operator">=</span> students<span class="token punctuation">.</span><span class="token function">OrderBy</span><span class="token punctuation">(</span>student <span class="token operator">=></span> student<span class="token punctuation">.</span>Age<span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 使用LINQ的OrderByDescending进行降序排序</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> result2 <span class="token operator">=</span> students<span class="token punctuation">.</span><span class="token function">OrderByDescending</span><span class="token punctuation">(</span>student <span class="token operator">=></span> student<span class="token punctuation">.</span>Age<span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
<!--rehype:className=wrap-text-->
</div></div></div><div class="wrap h3body-not-exist col-span-3"><div class="wrap-header h3wrap"><h3 id="join"><a aria-hidden="true" tabindex="-1" href="#join"><span class="icon icon-link"></span></a>JOIN</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-3-->
<ul>
<li><code>Join</code>：用于执行内连接操作，它会返回两个数据源中满足连接条件的元素的交集</li>
<li><code>GroupJoin</code>：用于执行左外连接（left outer join）操作，它会返回左边数据源的所有元素，以及每个元素所匹配的右边数据源的元素组成的集合。(嵌套)</li>
</ul>
<p>示例数据源</p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name">List<span class="token punctuation">&#x3C;</span>Department<span class="token punctuation">></span></span> departments <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">List<span class="token punctuation">&#x3C;</span>Department<span class="token punctuation">></span></span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Department</span> <span class="token punctuation">{</span> ID <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">,</span> Name <span class="token operator">=</span> <span class="token string">"HR"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Department</span> <span class="token punctuation">{</span> ID <span class="token operator">=</span> <span class="token number">2</span><span class="token punctuation">,</span> Name <span class="token operator">=</span> <span class="token string">"IT"</span> <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span><span class="token punctuation">;</span>
</span></code></pre>
<p>示例数据源</p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name">List<span class="token punctuation">&#x3C;</span>Employee<span class="token punctuation">></span></span> employees <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">List<span class="token punctuation">&#x3C;</span>Employee<span class="token punctuation">></span></span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Employee</span> <span class="token punctuation">{</span> DepartmentID <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">,</span> Name <span class="token operator">=</span> <span class="token string">"Alice"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Employee</span> <span class="token punctuation">{</span> DepartmentID <span class="token operator">=</span> <span class="token number">2</span><span class="token punctuation">,</span> Name <span class="token operator">=</span> <span class="token string">"Bob"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Employee</span> <span class="token punctuation">{</span> DepartmentID <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">,</span> Name <span class="token operator">=</span> <span class="token string">"Charlie"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Employee</span> <span class="token punctuation">{</span> DepartmentID <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">,</span> Name <span class="token operator">=</span> <span class="token string">"David"</span> <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span><span class="token punctuation">;</span>
</span></code></pre>
<p>使用 <code>Join</code>，将部门和员工相结合，获取部门名称和员工名称的集合</p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> joinQuery <span class="token operator">=</span> departments<span class="token punctuation">.</span><span class="token function">Join</span><span class="token punctuation">(</span>employees<span class="token punctuation">,</span> 
</span><span class="code-line">    department <span class="token operator">=></span> department<span class="token punctuation">.</span>ID<span class="token punctuation">,</span> employee <span class="token operator">=></span> employee<span class="token punctuation">.</span>DepartmentID<span class="token punctuation">,</span> 
</span><span class="code-line">    <span class="token punctuation">(</span>department<span class="token punctuation">,</span> employee<span class="token punctuation">)</span> <span class="token operator">=></span> <span class="token keyword">new</span> <span class="token punctuation">{</span> Department <span class="token operator">=</span> department<span class="token punctuation">.</span>Name<span class="token punctuation">,</span> Employee <span class="token operator">=</span> employee<span class="token punctuation">.</span>Name <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
<p>使用 <code>GroupJoin</code>，将部门和员工相结合，返回所有的部门，并返回每个部门相关联的员工集合(嵌套)</p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> groupJoinQuery <span class="token operator">=</span> departments<span class="token punctuation">.</span><span class="token function">GroupJoin</span><span class="token punctuation">(</span>employees<span class="token punctuation">,</span> 
</span><span class="code-line">    department <span class="token operator">=></span> department<span class="token punctuation">.</span>ID<span class="token punctuation">,</span> employee <span class="token operator">=></span> employee<span class="token punctuation">.</span>DepartmentID<span class="token punctuation">,</span> 
</span><span class="code-line">    <span class="token punctuation">(</span>department<span class="token punctuation">,</span> employeeGroup<span class="token punctuation">)</span> <span class="token operator">=></span> <span class="token keyword">new</span> 
</span><span class="code-line">        <span class="token punctuation">{</span> 
</span><span class="code-line">            Department <span class="token operator">=</span> department<span class="token punctuation">.</span>Name<span class="token punctuation">,</span> 
</span><span class="code-line">            Employees <span class="token operator">=</span> employeeGroup<span class="token punctuation">.</span><span class="token function">Select</span><span class="token punctuation">(</span>e <span class="token operator">=></span> e<span class="token punctuation">.</span>Name<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">ToList</span><span class="token punctuation">(</span><span class="token punctuation">)</span> 
</span><span class="code-line">        <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 style="background:#e91e63;" id="结果转换"><a aria-hidden="true" tabindex="-1" href="#结果转换"><span class="icon icon-link"></span></a>结果转换</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-2&style=background:#e91e63;-->
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// ToList(): 将结果转换为List集合。</span>
</span><span class="code-line"><span class="token class-name">List<span class="token punctuation">&#x3C;</span>Student<span class="token punctuation">></span></span> resultList <span class="token operator">=</span> result<span class="token punctuation">.</span><span class="token function">ToList</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// ToDictionary(): 将结果转换为Dictionary字典。</span>
</span><span class="code-line"><span class="token class-name">Dictionary<span class="token punctuation">&#x3C;</span><span class="token keyword">string</span><span class="token punctuation">,</span> <span class="token keyword">int</span><span class="token punctuation">></span></span> resultDictionary <span class="token operator">=</span> students
</span><span class="code-line">    <span class="token punctuation">.</span><span class="token function">ToDictionary</span><span class="token punctuation">(</span>student <span class="token operator">=></span> student<span class="token punctuation">.</span>Name<span class="token punctuation">,</span> student <span class="token operator">=></span> student<span class="token punctuation">.</span>Age<span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// ToArray(): 将结果转换为数组。</span>
</span><span class="code-line"><span class="token class-name">Student<span class="token punctuation">[</span><span class="token punctuation">]</span></span> resultArray <span class="token operator">=</span> result<span class="token punctuation">.</span><span class="token function">ToArray</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// First(): 获取结果中的第一个元素。</span>
</span><span class="code-line"><span class="token class-name">Student</span> firstStudent <span class="token operator">=</span> result<span class="token punctuation">.</span><span class="token function">First</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// FirstOrDefault(): 获取结果中的第一个元素，如果结果为空则返回默认值。</span>
</span><span class="code-line"><span class="token class-name">Student</span> firstStudent <span class="token operator">=</span> result<span class="token punctuation">.</span><span class="token function">FirstOrDefault</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="自定义扩展方法"><a aria-hidden="true" tabindex="-1" href="#自定义扩展方法"><span class="icon icon-link"></span></a>自定义扩展方法</h3><div class="wrap-body">
<pre class="wrap-text"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">class</span> <span class="token class-name">CustomExtensions</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token return-type class-name">IEnumerable<span class="token punctuation">&#x3C;</span>T<span class="token punctuation">></span></span> <span class="token generic-method"><span class="token function">CustomFilter</span><span class="token generic class-name"><span class="token punctuation">&#x3C;</span>T<span class="token punctuation">></span></span></span><span class="token punctuation">(</span><span class="token keyword">this</span> <span class="token class-name">IEnumerable<span class="token punctuation">&#x3C;</span>T<span class="token punctuation">></span></span> source<span class="token punctuation">,</span> <span class="token class-name">Func<span class="token punctuation">&#x3C;</span>T<span class="token punctuation">,</span> <span class="token keyword">bool</span><span class="token punctuation">></span></span> predicate<span class="token punctuation">)</span>
</span><span class="code-line">    <span class="token punctuation">{</span>
</span><span class="code-line">        <span class="token keyword">foreach</span> <span class="token punctuation">(</span><span class="token class-name"><span class="token keyword">var</span></span> item <span class="token keyword">in</span> source<span class="token punctuation">)</span>
</span><span class="code-line">        <span class="token punctuation">{</span>
</span><span class="code-line">            <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">predicate</span><span class="token punctuation">(</span>item<span class="token punctuation">)</span><span class="token punctuation">)</span>
</span><span class="code-line">            <span class="token punctuation">{</span>
</span><span class="code-line">                <span class="token keyword">yield</span> <span class="token keyword">return</span> item<span class="token punctuation">;</span>
</span><span class="code-line">            <span class="token punctuation">}</span>
</span><span class="code-line">        <span class="token punctuation">}</span>
</span><span class="code-line">    <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line"><span class="token comment">// 使用自定义扩展方法</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> filteredData <span class="token operator">=</span> students<span class="token punctuation">.</span><span class="token function">CustomFilter</span><span class="token punctuation">(</span>s <span class="token operator">=></span> s<span class="token punctuation">.</span>Age <span class="token operator">></span> <span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
<!--rehype:className=wrap-text-->
</div></div></div><div class="wrap h3body-not-exist col-span-3"><div class="wrap-header h3wrap"><h3 style="background:#e91e63;" id="示例"><a aria-hidden="true" tabindex="-1" href="#示例"><span class="icon icon-link"></span></a>示例</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-3&style=background:#e91e63;-->
<p>假设有一个包含学生信息的列表，每个学生有姓名、年龄和成绩。使用LINQ查询来选择年龄大于20岁的学生，然后按照他们的成绩进行分组，并选择每个分组中年龄最小的学生的姓名。</p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 示例数据源</span>
</span><span class="code-line"><span class="token class-name">List<span class="token punctuation">&#x3C;</span>Student<span class="token punctuation">></span></span> students <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">List<span class="token punctuation">&#x3C;</span>Student<span class="token punctuation">></span></span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Alice"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">25</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"A"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Bob"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">30</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"B"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Barry"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">35</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"C"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Charlie"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">22</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"A"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"David"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">21</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"C"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Damon"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">28</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"B"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token keyword">new</span> <span class="token constructor-invocation class-name">Student</span> <span class="token punctuation">{</span> Name <span class="token operator">=</span> <span class="token string">"Echo"</span><span class="token punctuation">,</span> Age <span class="token operator">=</span> <span class="token number">18</span><span class="token punctuation">,</span> Grade <span class="token operator">=</span> <span class="token string">"C"</span> <span class="token punctuation">}</span>
</span><span class="code-line"><span class="token punctuation">}</span><span class="token punctuation">;</span>
</span></code></pre>
<p>使用 <code>LINQ</code> 进行查询</p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">var</span></span> result <span class="token operator">=</span> students
</span><span class="code-line">    <span class="token punctuation">.</span><span class="token function">Where</span><span class="token punctuation">(</span>student <span class="token operator">=></span> student<span class="token punctuation">.</span>Age <span class="token operator">></span> <span class="token number">20</span><span class="token punctuation">)</span> <span class="token comment">// WHERE: 选择年龄大于20的学生</span>
</span><span class="code-line">    <span class="token punctuation">.</span><span class="token function">GroupBy</span><span class="token punctuation">(</span>student <span class="token operator">=></span> student<span class="token punctuation">.</span>Grade<span class="token punctuation">)</span>  <span class="token comment">// GROUP BY: 按成绩分组</span>
</span><span class="code-line">    <span class="token punctuation">.</span><span class="token function">Select</span><span class="token punctuation">(</span><span class="token keyword">group</span> <span class="token operator">=></span> <span class="token keyword">group</span><span class="token punctuation">.</span><span class="token function">OrderBy</span><span class="token punctuation">(</span>student <span class="token operator">=></span> student<span class="token punctuation">.</span>Age<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">First</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span>Name<span class="token punctuation">)</span> <span class="token comment">// SELECT: 选择每个分组中年龄最小的学生的姓名</span>
</span><span class="code-line">    <span class="token punctuation">.</span><span class="token function">ToList</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//转换为List&#x3C;Student>()</span>
</span></code></pre>
<p>输出结果</p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token punctuation">[</span><span class="token string">"Charlie"</span><span class="token punctuation">,</span><span class="token string">"Damon"</span><span class="token punctuation">,</span><span class="token string">"David"</span><span class="token punctuation">]</span>
</span></code></pre>
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="语法糖"><a aria-hidden="true" tabindex="-1" href="#语法糖"><span class="icon icon-link"></span></a>语法糖</h2><div class="wrap-body">
<blockquote>
<p>语法糖需要根据 <code>c#</code> 版本来确实是否可以使用，一般情况下 <code>c# 8.0</code> 及以上的 <code>C#</code> 版本都已支持。</p>
</blockquote>
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="对象判空及赋值"><a aria-hidden="true" tabindex="-1" href="#对象判空及赋值"><span class="icon icon-link"></span></a>对象判空及赋值</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-2-->
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 判断对象是否为空，为空抛出异常</span>
</span><span class="code-line"><span class="token keyword">if</span><span class="token punctuation">(</span>obj <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">NullReferenceException</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 简化的语法糖</span>
</span><span class="code-line">obj <span class="token operator">??</span> <span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name">NullReferenceException</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 判断 对象为空 的情况下再赋新值</span>
</span><span class="code-line"><span class="token comment">//     对象不为空 不进行赋值</span>
</span><span class="code-line"><span class="token keyword">if</span><span class="token punctuation">(</span>obj <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">  obj <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name"><span class="token keyword">object</span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 简化的语法糖</span>
</span><span class="code-line">obj <span class="token operator">??=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name"><span class="token keyword">object</span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="可空类型判空及赋值"><a aria-hidden="true" tabindex="-1" href="#可空类型判空及赋值"><span class="icon icon-link"></span></a>可空类型判空及赋值</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// 可空类型</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">int</span><span class="token punctuation">?</span></span> nums <span class="token operator">=</span> <span class="token keyword">null</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 判断值是否为空，并进行不同的赋值</span>
</span><span class="code-line"><span class="token keyword">if</span><span class="token punctuation">(</span>nums <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">  result <span class="token operator">=</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span> 
</span><span class="code-line"><span class="token keyword">else</span> 
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">  result <span class="token operator">=</span> nums<span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 简化的语法糖</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">int</span></span> result <span class="token operator">=</span> nums <span class="token operator">??</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="减少空引用"><a aria-hidden="true" tabindex="-1" href="#减少空引用"><span class="icon icon-link"></span></a>减少空引用</h3><div class="wrap-body">
<p>判断数组或 <code>list</code> 不能 <code>null</code> 且有元素</p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">if</span><span class="token punctuation">(</span>list <span class="token operator">!=</span> <span class="token keyword">null</span> <span class="token operator">&#x26;&#x26;</span> list<span class="token punctuation">.</span>Count <span class="token operator">></span> <span class="token number">0</span><span class="token punctuation">)</span>
</span></code></pre>
<p>简化的语法糖当 <code>list</code> 为 <code>null</code> 时，将直接返回 <code>false</code></p>
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">if</span><span class="token punctuation">(</span>list<span class="token punctuation">?.</span>Count <span class="token operator">></span> <span class="token number">0</span><span class="token punctuation">)</span>
</span></code></pre>
<p>同样可运用在赋值时，如果 <code>obj</code> 为 <code>null</code>，将不会取 <code>obj.text</code> 的值，而是将会为 <code>text</code> 赋值 <code>null</code></p>
<pre class="wrap-text"><code class="language-cs code-highlight"><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> text <span class="token operator">=</span> obj<span class="token punctuation">?.</span>text<span class="token punctuation">;</span>
</span></code></pre>
<!--rehype:className=wrap-text-->
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="判断参数类型并转换类型校验"><a aria-hidden="true" tabindex="-1" href="#判断参数类型并转换类型校验"><span class="icon icon-link"></span></a>判断参数类型并转换类型+校验</h3><div class="wrap-body">
<ul class="style-timeline">
<li>判断 <code>value</code> 是否为 <code>string</code> 类型，如果 <code>value</code> 是 <code>string</code> 类型</li>
<li>那么将 <code>value</code> 转换为 <code>string</code> 类型，并赋值给 <code>stringValue</code></li>
<li>再判断 <code>stringValue</code> 是否不为 <code>Null</code> 或 <code>空</code></li>
</ul>
<!--rehype:className=style-timeline-->
<pre class="wrap-text"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">if</span><span class="token punctuation">(</span><span class="token keyword">value</span> <span class="token keyword">is</span> <span class="token class-name"><span class="token keyword">string</span></span> stringValue <span class="token operator">&#x26;&#x26;</span> <span class="token operator">!</span><span class="token keyword">string</span><span class="token punctuation">.</span><span class="token function">IsNullOrEmpty</span><span class="token punctuation">(</span>stringValue<span class="token punctuation">)</span><span class="token punctuation">)</span>
</span></code></pre>
<!--rehype:className=wrap-text-->
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="switch"><a aria-hidden="true" tabindex="-1" href="#switch"><span class="icon icon-link"></span></a>Switch</h3><div class="wrap-body">
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token keyword">public</span> <span class="token return-type class-name"><span class="token keyword">string</span></span> <span class="token function">GetNums</span><span class="token punctuation">(</span><span class="token class-name"><span class="token keyword">int</span></span> num<span class="token punctuation">)</span>
</span><span class="code-line"><span class="token punctuation">{</span>
</span><span class="code-line">  <span class="token comment">// 使用这种方式的switch时，要求返回类型统一</span>
</span><span class="code-line">  <span class="token class-name"><span class="token keyword">string</span></span> str <span class="token operator">=</span> num <span class="token keyword">switch</span>
</span><span class="code-line">  <span class="token punctuation">{</span>
</span><span class="code-line">    <span class="token number">1</span> <span class="token operator">=></span> <span class="token string">"num的值是1"</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token number">2</span> <span class="token operator">=></span> <span class="token string">"num的值是2"</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token number">3</span> <span class="token operator">=></span> <span class="token string">"num的值是3"</span><span class="token punctuation">,</span>
</span><span class="code-line">    <span class="token number">4</span> <span class="token operator">=></span> <span class="token string">"num的值是4"</span><span class="token punctuation">,</span>
</span><span class="code-line">    _ <span class="token operator">=></span> <span class="token string">"其他"</span>
</span><span class="code-line">  <span class="token punctuation">}</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line">  <span class="token keyword">return</span> str<span class="token punctuation">;</span>
</span><span class="code-line"><span class="token punctuation">}</span>
</span></code></pre>
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="切片操作"><a aria-hidden="true" tabindex="-1" href="#切片操作"><span class="icon icon-link"></span></a>切片操作</h3><div class="wrap-body">
<!--rehype:wrap-class=col-span-2-->
<pre class="language-cs"><code class="language-cs code-highlight"><span class="code-line"><span class="token comment">// **以下所有[]中的数字都代表索引**</span>
</span><span class="code-line"><span class="token comment">// **如果是范围索引，且声明结束索引，那么都将不包含结束索引的值**</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 数组例子</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span><span class="token punctuation">[</span><span class="token punctuation">]</span></span> arr <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token constructor-invocation class-name"><span class="token keyword">string</span><span class="token punctuation">[</span><span class="token punctuation">]</span></span> <span class="token punctuation">{</span> <span class="token string">"10"</span><span class="token punctuation">,</span> <span class="token string">"20"</span><span class="token punctuation">,</span> <span class="token string">"30"</span><span class="token punctuation">,</span> <span class="token string">"40"</span><span class="token punctuation">,</span> <span class="token string">"50"</span><span class="token punctuation">,</span> <span class="token string">"60"</span><span class="token punctuation">,</span> <span class="token string">"70"</span><span class="token punctuation">,</span> <span class="token string">"80"</span><span class="token punctuation">,</span> <span class="token string">"90"</span><span class="token punctuation">,</span> <span class="token string">"100"</span> <span class="token punctuation">}</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 获取最后一个元素</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span></span> str <span class="token operator">=</span> arr<span class="token punctuation">[</span><span class="token operator">^</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 获取前3个元素，从索引0开始 到 索引3(不包含)：["10","20","30"]</span>
</span><span class="code-line"><span class="token comment">// 可省略索引0，从开始 到 索引3(不包含)</span>
</span><span class="code-line"><span class="token comment">// string[] strs = arr[..3];</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span><span class="token punctuation">[</span><span class="token punctuation">]</span></span> strs1 <span class="token operator">=</span> arr<span class="token punctuation">[</span><span class="token number">0</span><span class="token range operator">..</span><span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 获取后3个元素，从倒数第3个元素开始 到 最后：["80", "90", "100"]</span>
</span><span class="code-line"><span class="token comment">// 最后一位索引被省略 string[] strs21 = arr[^3..^0];</span>
</span><span class="code-line"><span class="token comment">// ^0 倒数第0个元素是不存在的</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span><span class="token punctuation">[</span><span class="token punctuation">]</span></span> strs2 <span class="token operator">=</span> arr<span class="token punctuation">[</span><span class="token operator">^</span><span class="token number">3</span><span class="token range operator">..</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 指定获取 正向 某一段元素</span>
</span><span class="code-line"><span class="token comment">// 从索引3开始 到 索引7(不包含)：["40", "50", "60", "70"]</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span><span class="token punctuation">[</span><span class="token punctuation">]</span></span> strs3 <span class="token operator">=</span> arr<span class="token punctuation">[</span><span class="token number">3</span><span class="token range operator">..</span><span class="token number">7</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
</span><span class="code-line">
</span><span class="code-line"><span class="token comment">// 指定获取 反向 某一段元素</span>
</span><span class="code-line"><span class="token comment">// 倒数第4个元素开始 到 倒数第2个元素(不包含)：["70","80"]</span>
</span><span class="code-line"><span class="token class-name"><span class="token keyword">string</span><span class="token punctuation">[</span><span class="token punctuation">]</span></span> strs4 <span class="token operator">=</span> arr<span class="token punctuation">[</span><span class="token operator">^</span><span class="token number">4</span><span class="token range operator">..</span><span class="token operator">^</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
</span></code></pre>
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="杂项"><a aria-hidden="true" tabindex="-1" href="#杂项"><span class="icon icon-link"></span></a>杂项</h2><div class="wrap-body">
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist col-span-3"><div class="wrap-header h3wrap"><h3 id="常用-net-概念"><a aria-hidden="true" tabindex="-1" href="#常用-net-概念"><span class="icon icon-link"></span></a>常用 .NET 概念</h3><div class="wrap-body">
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<table class="show-header left-align"><thead><tr><th align="left">概念</th><th>中文名</th><th>定义</th></tr></thead><tbody><tr><td align="left"><code>Runtime</code></td><td>运行时</td><td>执行给定的已编译代码单元所需的服务集合</td></tr><tr><td align="left"><code>Common Language Runtime (CLR)</code></td><td>通用语言运行库</td><td>主要定位、加载和托管 .NET 对象。<br>CLR 还处理内存管理、应用程序托管、线程协调、执行安全检查和其他低级细节</td></tr><tr><td align="left"><code>Managed code</code></td><td>托管代码</td><td>在 <code>.NET</code> 运行时编译和运行的代码。 C#/F#/VB 就是例子</td></tr><tr><td align="left"><code>Unmanaged code</code></td><td>非托管代码</td><td>直接编译为机器代码且不能由 .NET 运行时直接托管的代码。<br>不包含空闲内存管理、垃圾收集等。从 C/C++ 创建的 DLL 就是示例</td></tr></tbody></table>
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